Storage Foundation 7.4.1 Administrator's Guide - Linux

Last Published:
Product(s): InfoScale & Storage Foundation (7.4.1)
Platform: Linux
  1. Section I. Introducing Storage Foundation
    1. Overview of Storage Foundation
      1.  
        About Storage Foundation
      2.  
        About Dynamic Multi-Pathing (DMP)
      3.  
        About Veritas Volume Manager
      4. About Veritas File System
        1.  
          About the Veritas File System intent log
        2.  
          About extents
        3.  
          About file system disk layouts
      5. About Storage Foundation Cluster File System (SFCFS)
        1. About Veritas File System features supported in cluster file systems
          1.  
            Veritas File System features not in cluster file systems
      6.  
        About Veritas InfoScale Operations Manager
      7. About Veritas Replicator
        1.  
          What is VFR?
        2.  
          Features of VFR
      8.  
        Use cases for Storage Foundation
    2. How Dynamic Multi-Pathing works
      1. How DMP works
        1. Device discovery
          1.  
            About enclosure-based naming
        2. How DMP monitors I/O on paths
          1. Path failover mechanism
            1.  
              Subpaths Failover Group (SFG)
            2.  
              Low Impact Path Probing (LIPP)
          2.  
            I/O throttling
        3.  
          Load balancing
        4. DMP in a clustered environment
          1.  
            About enabling or disabling controllers with shared disk groups
      2.  
        Veritas Volume Manager co-existence with Oracle Automatic Storage Management disks
    3. How Veritas Volume Manager works
      1. How Veritas Volume Manager works with the operating system
        1.  
          How data is stored
      2. How Veritas Volume Manager handles storage management
        1. Physical objects
          1.  
            About disk partitions
          2.  
            Disk arrays
        2. Virtual objects
          1.  
            Combining virtual objects in Veritas Volume Manager
        3.  
          About the configuration daemon in Veritas Volume Manager
        4.  
          Multiple paths to disk arrays
      3. Volume layouts in Veritas Volume Manager
        1.  
          Non-layered volumes
        2.  
          Layered volumes
        3.  
          Layout methods
        4.  
          Concatenation, spanning, and carving
        5.  
          Striping (RAID-0)
        6.  
          Mirroring (RAID-1)
        7.  
          Striping plus mirroring (mirrored-stripe or RAID-0+1)
        8.  
          Mirroring plus striping (striped-mirror, RAID-1+0, or RAID-10)
        9. RAID-5 (striping with parity)
          1.  
            Traditional RAID-5 arrays
          2.  
            Veritas Volume Manager RAID-5 arrays
          3.  
            Left-symmetric layout
          4.  
            RAID-5 logging
          5.  
            About layered volumes
      4. Online relayout
        1.  
          How online relayout works
        2.  
          Limitations of online relayout
        3.  
          Transformation characteristics
        4.  
          Transformations and volume length
      5. Volume resynchronization
        1.  
          Dirty flags
        2.  
          Resynchronization process
      6.  
        Hot-relocation
      7. Dirty region logging
        1.  
          Log subdisks and plexes
        2.  
          Sequential DRL
      8. Volume snapshots
        1.  
          Comparison of snapshot features
      9.  
        Support for atomic writes
      10. FastResync
        1.  
          How FastResync works
        2.  
          How non-persistent FastResync works with snapshots
        3.  
          How persistent FastResync works with snapshots
        4. DCO volume versioning
          1.  
            Instant snap (version 20) DCO volume layout
          2.  
            Version 0 DCO volume layout
        5.  
          Effect of growing a volume on the FastResync map
        6.  
          FastResync limitations
      11.  
        Volume sets
      12. How VxVM handles hardware clones or snapshots
        1.  
          How VxVM uses the unique disk identifier (UDID)
      13. Volume encryption
        1.  
          Using passphrases for encryption
        2.  
          Using Key Management Server for encryption
        3.  
          Recommendations for encryption
    4. How Veritas File System works
      1.  
        Veritas File System features
      2. Veritas File System performance enhancements
        1. Enhanced I/O performance
          1.  
            Enhanced I/O clustering
          2.  
            Veritas Volume Manager integration with Veritas File System for enhanced I/O performance
          3.  
            Application-specific parameters for enhanced I/O performance
        2.  
          Delayed allocation for extending writes
      3. Using Veritas File System
        1. Online system administration
          1.  
            About defragmentation
          2.  
            About file system resizing
        2. Application program interface
          1.  
            Expanded application facilities
  2. Section II. Provisioning storage
    1. Provisioning new storage
      1.  
        Provisioning new storage
      2.  
        Growing the existing storage by adding a new LUN
      3.  
        Growing the existing storage by growing the LUN
      4.  
        Displaying SF information with vxlist
    2. Advanced allocation methods for configuring storage
      1. Customizing allocation behavior
        1.  
          Setting default values for vxassist
        2. Using rules to make volume allocation more efficient
          1.  
            Rule file format
          2.  
            Using rules to create a volume
        3. Understanding persistent attributes
          1.  
            Using persistent attributes
        4. Customizing disk classes for allocation
          1.  
            User-defined alias names for disk classes
          2.  
            User-defined precedence order for disk classes
          3.  
            User-defined disk classes
        5. Specifying allocation constraints for vxassist operations with the use clause and the require clause
          1.  
            About require constraints
          2.  
            About use constraints
          3.  
            Interaction of multiple require and use constraints
          4.  
            Examples of use and require constraints
        6.  
          Management of the use and require type of persistent attributes
      2. Creating volumes of a specific layout
        1.  
          Types of volume layouts
        2. Creating a mirrored volume
          1.  
            Creating a mirrored-concatenated volume
          2.  
            Creating a concatenated-mirror volume
        3. Creating a striped volume
          1.  
            Creating a mirrored-stripe volume
          2.  
            Creating a striped-mirror volume
        4.  
          Creating a RAID-5 volume
      3.  
        Creating a volume on specific disks
      4.  
        Creating volumes on specific media types
      5.  
        Creating encrypted volumes
      6.  
        Changing the encryption password
      7.  
        Viewing encrypted volumes
      8.  
        Automating startup for encrypted volumes
      9.  
        Configuring a Key Management Server
      10.  
        Specifying ordered allocation of storage to volumes
      11.  
        Site-based allocation
      12.  
        Changing the read policy for mirrored volumes
    3. Creating and mounting VxFS file systems
      1. Creating a VxFS file system
        1.  
          File system block size
        2.  
          Intent log size
      2.  
        Converting a file system to VxFS
      3. Mounting a VxFS file system
        1.  
          log mount option
        2.  
          delaylog mount option
        3. tmplog mount option
          1.  
            Logging mode persistence guarantees
        4.  
          logiosize mount option
        5.  
          nodatainlog mount option
        6.  
          blkclear mount option
        7.  
          mincache mount option
        8.  
          convosync mount option
        9. ioerror mount option
          1.  
            disable policy
          2.  
            wdisable policy and mwdisable policy
          3.  
            mdisable policy
        10. largefiles and nolargefiles mount options
          1.  
            Creating a file system with large files
          2.  
            Mounting a file system with large files
          3.  
            Managing a file system with large files
        11.  
          cio mount option
        12.  
          mntlock mount option
        13.  
          ckptautomnt mount option
        14.  
          Combining mount command options
      4.  
        Unmounting a file system
      5. Resizing a file system
        1.  
          Extending a file system using fsadm
        2.  
          Shrinking a file system
        3.  
          Reorganizing a file system
      6.  
        Displaying information on mounted file systems
      7.  
        Identifying file system types
      8. Monitoring free space
        1.  
          Monitoring fragmentation
    4. Extent attributes
      1. About extent attributes
        1.  
          Reservation: preallocating space to a file
        2.  
          Fixed extent size
        3.  
          How the fixed extent size works with the shared extents
        4. Other extent attribute controls
          1.  
            Extent attribute alignment
          2.  
            Extent attribute contiguity
          3.  
            Write operations beyond extent attribute reservation
          4.  
            Extent attribute reservation trimming
          5.  
            Extent attribute reservation persistence
          6.  
            Including an extent attribute reservation in the file
      2. Commands related to extent attributes
        1.  
          About failing to preserve extent attributes
  3. Section III. Administering multi-pathing with DMP
    1. Administering Dynamic Multi-Pathing
      1. Discovering and configuring newly added disk devices
        1.  
          Partial device discovery
        2. About discovering disks and dynamically adding disk arrays
          1.  
            How DMP claims devices
          2.  
            Disk categories
          3.  
            Adding DMP support for a new disk array
          4.  
            Enabling discovery of new disk arrays
        3.  
          About third-party driver coexistence
        4. How to administer the Device Discovery Layer
          1.  
            Listing all the devices including iSCSI
          2.  
            Listing all the Host Bus Adapters including iSCSI
          3.  
            Listing the ports configured on a Host Bus Adapter
          4.  
            Listing the targets configured from a Host Bus Adapter or a port
          5.  
            Listing the devices configured from a Host Bus Adapter and target
          6.  
            Getting or setting the iSCSI operational parameters
          7.  
            Listing all supported disk arrays
          8.  
            Displaying details about an Array Support Library
          9.  
            Excluding support for a disk array library
          10.  
            Re-including support for an excluded disk array library
          11.  
            Listing excluded disk arrays
          12.  
            Listing disks claimed in the DISKS category
          13.  
            Adding unsupported disk arrays to the DISKS category
          14.  
            Removing disks from the DISKS category
          15.  
            Foreign devices
      2.  
        Making devices invisible to VxVM
      3.  
        Making devices visible to VxVM
      4.  
        About enabling and disabling I/O for controllers and storage processors
      5.  
        About displaying DMP database information
      6.  
        Displaying the paths to a disk
      7. Administering DMP using the vxdmpadm utility
        1.  
          Retrieving information about a DMP node
        2.  
          Displaying consolidated information about the DMP nodes
        3.  
          Displaying the members of a LUN group
        4.  
          Displaying paths controlled by a DMP node, controller, enclosure, or array port
        5.  
          Displaying information about controllers
        6.  
          Displaying information about enclosures
        7.  
          Displaying information about array ports
        8.  
          Displaying information about devices controlled by third-party drivers
        9.  
          Displaying extended device attributes
        10.  
          Suppressing or including devices from VxVM control
        11. Gathering and displaying I/O statistics
          1.  
            Displaying cumulative I/O statistics
          2.  
            Displaying statistics for queued or erroneous I/Os
          3.  
            Examples of using the vxdmpadm iostat command
        12.  
          Setting the attributes of the paths to an enclosure
        13.  
          Displaying the redundancy level of a device or enclosure
        14.  
          Specifying the minimum number of active paths
        15.  
          Displaying the I/O policy
        16. Specifying the I/O policy
          1.  
            Scheduling I/O on the paths of an Asymmetric Active/Active or an ALUA array
          2.  
            Example of applying load balancing in a SAN
        17.  
          Disabling I/O for paths, controllers, array ports, or DMP nodes
        18.  
          Enabling I/O for paths, controllers, array ports, or DMP nodes
        19.  
          Renaming an enclosure
        20.  
          Configuring the response to I/O failures
        21.  
          Configuring the I/O throttling mechanism
        22.  
          Configuring Low Impact Path Probing (LIPP)
        23.  
          Configuring Subpaths Failover Groups (SFG)
        24.  
          Displaying recovery option values
        25.  
          Configuring DMP path restoration policies
        26.  
          Stopping the DMP path restoration thread
        27.  
          Displaying the status of the DMP path restoration thread
        28.  
          Configuring Array Policy Modules
    2. Dynamic Reconfiguration of devices
      1.  
        About online dynamic reconfiguration
      2. Reconfiguring a LUN online that is under DMP control using the Dynamic Reconfiguration tool
        1.  
          Removing LUNs dynamically from an existing target ID
        2.  
          Adding new LUNs dynamically to a target ID
        3.  
          Replacing LUNs dynamically from an existing target ID
        4.  
          Replacing a host bus adapter online
      3. Manually reconfiguring a LUN online that is under DMP control
        1.  
          Overview of manually reconfiguring a LUN
        2.  
          Manually removing LUNs dynamically from an existing target ID
        3.  
          Manually adding new LUNs dynamically to a new target ID
        4.  
          About detecting target ID reuse if the operating system device tree is not cleaned up
        5.  
          Scanning an operating system device tree after adding or removing LUNs
        6.  
          Manually cleaning up the operating system device tree after removing LUNs
      4.  
        Changing the characteristics of a LUN from the array side
      5.  
        Upgrading the array controller firmware online
      6.  
        Reformatting NVMe devices manually
    3. Managing devices
      1. Displaying disk information
        1.  
          About Media Format Discovery
        2.  
          Viewing information about the native layouts of operating system
        3. Viewing information about the disk sector size
          1.  
            Supported operating systems
        4.  
          Displaying disk information with vxdiskadm
      2. Changing the disk device naming scheme
        1.  
          Displaying the disk-naming scheme
        2.  
          Setting customized names for DMP nodes
        3.  
          Regenerating persistent device names
        4.  
          Changing device naming for enclosures controlled by third-party drivers
        5. About the Array Volume Identifier (AVID) attribute
          1.  
            Enclosure based naming with the Array Volume Identifier (AVID) attribute
      3.  
        About disk installation and formatting
      4. Adding and removing disks
        1. Adding a disk to VxVM
          1.  
            Disk reinitialization
          2.  
            Using vxdiskadd to put a disk under VxVM control
        2. Removing disks
          1.  
            Removing a disk with subdisks
          2.  
            Removing a disk with no subdisks
      5.  
        Renaming a disk
    4. Event monitoring
      1.  
        About the Dynamic Multi-Pathing (DMP) event source daemon (vxesd)
      2.  
        Fabric Monitoring and proactive error detection
      3.  
        Dynamic Multi-Pathing (DMP) discovery of iSCSI and SAN Fibre Channel topology
      4.  
        DMP event logging
      5.  
        Starting and stopping the Dynamic Multi-Pathing (DMP) event source daemon
  4. Section IV. Administering Storage Foundation
    1. Administering sites and remote mirrors
      1. About sites and remote mirrors
        1.  
          About site-based allocation
        2.  
          About site consistency
        3.  
          About site tags
        4.  
          About the site read policy
      2.  
        Making an existing disk group site consistent
      3.  
        Configuring a new disk group as a Remote Mirror configuration
      4. Fire drill - testing the configuration
        1.  
          Simulating site failure
        2.  
          Verifying the secondary site
        3.  
          Recovery from simulated site failure
      5. Changing the site name
        1.  
          Resetting the site name for a host
      6. Administering the Remote Mirror configuration
        1.  
          Configuring site tagging for disks or enclosures
        2.  
          Configuring automatic site tagging for a disk group
        3.  
          Configuring site consistency on a volume
      7.  
        Examples of storage allocation by specifying sites
      8.  
        Displaying site information
      9. Failure and recovery scenarios
        1.  
          Recovering from a loss of site connectivity
        2.  
          Recovering from storage failure
        3.  
          Recovering from site failure
        4.  
          Recovering from disruption to connectivity to storage at all sites from the hosts at a site
        5.  
          Automatic site reattachment
  5. Section V. Optimizing I/O performance
    1. Veritas File System I/O
      1.  
        About Veritas File System I/O
      2. Buffered and Direct I/O
        1. Direct I/O
          1.  
            Direct I/O requirements
          2.  
            Direct I/O versus synchronous I/O
          3.  
            Direct I/O CPU overhead
          4.  
            Discovered Direct I/O
        2.  
          Unbuffered I/O
        3. Data synchronous I/O
          1.  
            Data synchronous I/O vs. synchronous I/O
      3.  
        Concurrent I/O
      4.  
        Cache advisories
      5.  
        Freezing and thawing a file system
      6.  
        Getting the I/O size
      7.  
        About Veritas InfoScale product components database accelerators
    2. Veritas Volume Manager I/O
      1.  
        Veritas Volume Manager throttling of administrative I/O
      2. Managing application I/O workloads using maximum IOPS settings
        1.  
          About application volume groups
        2.  
          Creating application volume groups
        3.  
          Viewing the list of application volume groups
        4.  
          Setting the maximum IOPS threshold on application volume groups
        5.  
          Viewing the IOPS statistics for application volume groups
        6.  
          Removing the maximum IOPS setting from application volume groups
        7.  
          Adding volumes to an application volume group
        8.  
          Removing volumes from an application volume group
        9.  
          Removing an application volume group
  6. Section VI. Using Point-in-time copies
    1. Understanding point-in-time copy methods
      1.  
        About point-in-time copies
      2. When to use point-in-time copies
        1.  
          Implementing point-in time copy solutions on a primary host
        2.  
          Implementing off-host point-in-time copy solutions
      3. About Storage Foundation point-in-time copy technologies
        1.  
          Comparison of Point-in-time copy solutions
      4. Volume-level snapshots
        1.  
          Persistent FastResync of volume snapshots
        2.  
          Data integrity in volume snapshots
        3.  
          Third-mirror break-off snapshots
        4. Space-optimized instant volume snapshots
          1.  
            How space-optimized instant snapshots work
        5.  
          Choices for snapshot resynchronization
        6.  
          Disk group split/join
      5. Storage Checkpoints
        1.  
          How Storage Checkpoints differ from snapshots
        2. How a Storage Checkpoint works
          1.  
            Copy-on-write
          2. Storage Checkpoint visibility
            1.  
              Storage Checkpoints and 64-bit inode numbers
        3. Types of Storage Checkpoints
          1.  
            Data Storage Checkpoints
          2.  
            Nodata Storage Checkpoints
          3.  
            Removable Storage Checkpoints
          4.  
            Non-mountable Storage Checkpoints
      6. About FileSnaps
        1.  
          Properties of FileSnaps
        2.  
          Concurrent I/O to FileSnaps
        3.  
          Copy-on-write and FileSnaps
        4.  
          Reading from FileSnaps
        5.  
          Block map fragmentation and FileSnaps
        6.  
          Backup and FileSnaps
      7. About snapshot file systems
        1.  
          How a snapshot file system works
    2. Administering volume snapshots
      1.  
        About volume snapshots
      2. Traditional third-mirror break-off snapshots
        1. Creating traditional third-mirror break-off snapshots
          1.  
            Converting a plex into a snapshot plex
          2.  
            Creating multiple snapshots with the vxassist command
          3.  
            Reattaching a snapshot volume
          4.  
            Adding plexes to a snapshot volume
          5.  
            Dissociating a snapshot volume
          6.  
            Displaying snapshot information
      3. Full-sized instant snapshots
        1. Creating instant snapshots
          1. Adding an instant snap DCO and DCO volume
            1.  
              Creating a shared cache object
            2.  
              Creating a volume for use as a full-sized instant or linked break-off snapshot
            3.  
              Upgrading the instant snap Data Change Objects (DCOs) and DCO volumes for a VxVM volume
          2.  
            Creating and managing space-optimized instant snapshots
          3.  
            Creating and managing full-sized instant snapshots
          4.  
            Creating and managing third-mirror break-off snapshots
          5.  
            Creating and managing linked break-off snapshot volumes
          6.  
            Creating multiple instant snapshots
          7.  
            Creating instant snapshots of volume sets
          8.  
            Adding snapshot mirrors to a volume
          9.  
            Removing a snapshot mirror
          10.  
            Removing a linked break-off snapshot volume
          11.  
            Adding a snapshot to a cascaded snapshot hierarchy
          12.  
            Refreshing an instant space-optimized snapshot
          13.  
            Reattaching an instant full-sized or plex break-off snapshot
          14.  
            Reattaching a linked break-off snapshot volume
          15.  
            Restoring a volume from an instant space-optimized snapshot
          16.  
            Dissociating an instant snapshot
          17.  
            Removing an instant snapshot
          18.  
            Splitting an instant snapshot hierarchy
          19.  
            Displaying instant snapshot information
          20. Controlling instant snapshot synchronization
            1.  
              Improving the performance of snapshot synchronization
          21.  
            Listing the snapshots created on a cache
          22.  
            Tuning the autogrow attributes of a cache
          23.  
            Monitoring and displaying cache usage
          24.  
            Growing and shrinking a cache
          25.  
            Removing a cache
      4.  
        Linked break-off snapshots
      5. Cascaded snapshots
        1.  
          Creating a snapshot of a snapshot
      6.  
        Creating multiple snapshots
      7.  
        Restoring the original volume from a snapshot
      8. Adding a version 0 DCO and DCO volume
        1.  
          Specifying storage for version 0 DCO plexes
        2.  
          Removing a version 0 DCO and DCO volume
        3.  
          Reattaching a version 0 DCO and DCO volume
    3. Administering Storage Checkpoints
      1.  
        About Storage Checkpoints
      2. Storage Checkpoint administration
        1.  
          Creating a Storage Checkpoint
        2.  
          Removing a Storage Checkpoint
        3.  
          Accessing a Storage Checkpoint
        4. Converting a data Storage Checkpoint to a nodata Storage Checkpoint
          1.  
            Showing the difference between a data and a nodata Storage Checkpoint
          2.  
            Converting multiple Storage Checkpoints
          3.  
            Creating a delayed nodata Storage Checkpoint
        5.  
          Enabling and disabling Storage Checkpoint visibility
      3.  
        Storage Checkpoint space management considerations
      4.  
        Restoring from a Storage Checkpoint
      5.  
        Storage Checkpoint quotas
    4. Administering FileSnaps
      1. FileSnap creation
        1.  
          FileSnap creation over Network File System
      2.  
        Using FileSnaps
      3. Using FileSnaps to create point-in-time copies of files
        1.  
          Using FileSnaps to provision virtual desktops
        2.  
          Using FileSnaps to optimize write intensive applications for virtual machines
        3.  
          Using FileSnaps to create multiple copies of data instantly
        4.  
          An example to perform FileSnap
      4.  
        Comparison of the logical size output of the fsadm -S shared, du, and df commands
    5. Administering snapshot file systems
      1.  
        Snapshot file system backups
      2.  
        Snapshot file system performance
      3.  
        About snapshot file system disk structure
      4.  
        Differences between snapshots and Storage Checkpoints
      5.  
        Creating a snapshot file system
  7. Section VII. Optimizing storage with Storage Foundation
    1. Understanding storage optimization solutions in Storage Foundation
      1.  
        About thin provisioning
      2.  
        About thin optimization solutions in Storage Foundation
      3. About SmartMove
        1.  
          SmartMove for thin provisioning
      4.  
        About the Thin Reclamation feature
      5.  
        About reclaiming space on Solid State Devices (SSDs) with the TRIM operation
      6.  
        Determining when to reclaim space on a thin reclamation LUN
      7.  
        How automatic reclamation works
    2. Migrating data from thick storage to thin storage
      1.  
        About using SmartMove to migrate to Thin Storage
      2.  
        Migrating to thin provisioning
    3. Maintaining Thin Storage with Thin Reclamation
      1. Reclamation of storage on thin reclamation arrays
        1.  
          About Thin Reclamation of a disk, a disk group, or an enclosure
        2.  
          About Thin Reclamation of a file system
      2. Identifying thin and thin reclamation LUNs
        1.  
          Displaying detailed information about reclamation commands
      3.  
        Displaying VxFS file system usage on thin reclamation LUNs
      4.  
        Reclaiming space on a file system
      5.  
        Reclaiming space on a disk, disk group, or enclosure
      6.  
        About the reclamation log file
      7.  
        Monitoring Thin Reclamation using the vxtask command
      8.  
        Configuring automatic reclamation
    4. Veritas InfoScale 4k sector device support solution
      1.  
        About 4K sector size technology
      2.  
        Veritas InfoScale unsupported configurations
      3.  
        Migrating VxFS file system from 512-bytes sector size devices to 4K sector size devices
  8. Section VIII. Maximizing storage utilization
    1. Understanding storage tiering with SmartTier
      1. About SmartTier
        1.  
          About VxFS multi-volume file systems
        2.  
          About VxVM volume sets
        3.  
          About volume tags
        4.  
          SmartTier file management
        5.  
          SmartTier sub-file object management
      2.  
        How the SmartTier policy works with the shared extents
      3.  
        SmartTier in a High Availability (HA) environment
    2. Creating and administering volume sets
      1.  
        About volume sets
      2.  
        Creating a volume set
      3.  
        Adding a volume to a volume set
      4.  
        Removing a volume from a volume set
      5.  
        Listing details of volume sets
      6.  
        Stopping and starting volume sets
      7. Managing raw device nodes of component volumes
        1.  
          Enabling raw device access when creating a volume set
        2.  
          Displaying the raw device access settings for a volume set
        3.  
          Controlling raw device access for an existing volume set
    3. Multi-volume file systems
      1.  
        About multi-volume file systems
      2.  
        About volume types
      3. Features implemented using multi-volume file system (MVFS) support
        1.  
          Volume availability
      4.  
        Creating multi-volume file systems
      5.  
        Converting a single volume file system to a multi-volume file system
      6. Adding a volume to and removing a volume from a multi-volume file system
        1.  
          Adding a volume to a multi-volume file system
        2.  
          Removing a volume from a multi-volume file system
        3.  
          Forcibly removing a volume in a multi-volume file system
        4.  
          Moving volume 0 in a multi-volume file system
      7. Volume encapsulation
        1.  
          Encapsulating a volume
        2.  
          Deencapsulating a volume
      8.  
        Reporting file extents
      9. Load balancing
        1.  
          Defining and assigning a load balancing allocation policy
        2.  
          Rebalancing extents
      10.  
        Converting a multi-volume file system to a single volume file system
    4. Administering SmartTier
      1. About SmartTier
        1.  
          About compressing files with SmartTier
      2.  
        Supported SmartTier document type definitions
      3. Placement classes
        1.  
          Tagging volumes as placement classes
        2.  
          Listing placement classes
      4. Administering placement policies
        1.  
          Assigning a placement policy
        2.  
          Unassigning a placement policy
        3.  
          Analyzing the space impact of enforcing a placement policy
        4.  
          Querying which files will be affected by enforcing a placement policy
        5.  
          Enforcing a placement policy
        6.  
          Validating a placement policy
      5.  
        File placement policy grammar
      6. File placement policy rules
        1.  
          SELECT statement
        2.  
          CREATE statement
        3. RELOCATE statement
          1.  
            Specifying the I/O temperature relocation criterion
          2.  
            Prefer attribute
          3.  
            Average I/O activity criteria
          4.  
            RELOCATE statement examples
        4. DELETE statement
          1.  
            DELETE statement examples
        5. COMPRESS statement
          1.  
            Specifying the I/O temperature compression criterion
          2.  
            Prefer attribute
          3.  
            Average I/O activity criteria
          4.  
            COMPRESS statement examples
        6. UNCOMPRESS statement
          1.  
            Specifying the I/O temperature uncompression criterion
          2.  
            Prefer attribute
          3.  
            Average I/O activity criteria
          4.  
            UNCOMPRESS statement examples
      7.  
        Calculating I/O temperature and access temperature
      8. Multiple criteria in file placement policy rule statements
        1.  
          Multiple file selection criteria in SELECT statement clauses
        2.  
          Multiple placement classes in <ON> clauses of CREATE statements and in <TO> clauses of RELOCATE statements
        3.  
          Multiple placement classes in <FROM> clauses of RELOCATE and DELETE statements
        4.  
          Multiple conditions in <WHEN> clauses of RELOCATE and DELETE statements
      9.  
        File placement policy rule and statement ordering
      10.  
        File placement policies and extending files
      11. Using SmartTier with solid state disks
        1.  
          Fine grain temperatures with solid state disks
        2.  
          Prefer mechanism with solid state disks
        3.  
          Average I/O activity with solid state disks
        4.  
          Frequent SmartTier scans with solid state disks
        5.  
          Quick identification of cold files with solid state disks
        6.  
          Example placement policy when using solid state disks
      12. Sub-file relocation
        1.  
          Moving sub-file data of files to specific target tiers
    5. Administering hot-relocation
      1.  
        About hot-relocation
      2. How hot-relocation works
        1.  
          Partial disk failure mail messages
        2.  
          Complete disk failure mail messages
        3.  
          How space is chosen for relocation
      3.  
        Configuring a system for hot-relocation
      4.  
        Displaying spare disk information
      5.  
        Marking a disk as a hot-relocation spare
      6.  
        Removing a disk from use as a hot-relocation spare
      7.  
        Excluding a disk from hot-relocation use
      8.  
        Making a disk available for hot-relocation use
      9.  
        Configuring hot-relocation to use only spare disks
      10. Moving relocated subdisks
        1. Moving relocated subdisks using vxunreloc
          1.  
            Moving hot-relocated subdisks back to their original disk
          2.  
            Moving hot-relocated subdisks back to a different disk
          3.  
            Forcing hot-relocated subdisks to accept different offsets
          4.  
            Examining which subdisks were hot-relocated from a disk
        2.  
          Restarting vxunreloc after errors
      11.  
        Modifying the behavior of hot-relocation
    6. Deduplicating data
      1. About deduplicating data
        1.  
          About deduplication chunk size
        2.  
          Deduplication and file system performance
        3.  
          About the deduplication scheduler
      2. Deduplicating data
        1.  
          Enabling and disabling deduplication on a file system
        2.  
          Scheduling deduplication of a file system
        3.  
          Performing a deduplication dry run
        4.  
          Querying the deduplication status of a file system
        5.  
          Starting and stopping the deduplication scheduler daemon
      3.  
        Deduplication results
      4.  
        Deduplication supportability
      5.  
        Deduplication use cases
      6.  
        Deduplication limitations
    7. Compressing files
      1. About compressing files
        1.  
          About the compressed file format
        2.  
          About the file compression attributes
        3.  
          About the file compression block size
      2.  
        Compressing files with the vxcompress command
      3.  
        Interaction of compressed files and other commands
      4.  
        Interaction of compressed files and other features
      5.  
        Interaction of compressed files and applications
      6. Use cases for compressing files
        1. Compressed files and databases
          1.  
            Supported database versions and environment
          2.  
            Compressing archive logs
          3.  
            Compressing read-only tablespaces
          4.  
            Compressing infrequently accessed table partitions
          5.  
            Compressing infrequently accessed datafiles
          6.  
            Best practices for compressing files in an Oracle database
        2.  
          Compressing all files that meet the specified criteria
  9. Section IX. Administering storage
    1. Managing volumes and disk groups
      1. Rules for determining the default disk group
        1.  
          Displaying the system-wide boot disk group
        2.  
          Displaying and specifying the system-wide default disk group
      2. Moving volumes or disks
        1.  
          Moving volumes from a VxVM disk
        2.  
          Moving disks between disk groups
        3. Reorganizing the contents of disk groups
          1.  
            Limitations of disk group split and join
          2. Listing objects potentially affected by a move
            1.  
              Moving DCO volumes between disk groups
          3.  
            Moving objects between disk groups
          4.  
            Splitting disk groups
          5.  
            Joining disk groups
      3. Monitoring and controlling tasks
        1.  
          Specifying task tags
        2. Managing tasks with vxtask
          1.  
            vxtask operations
          2.  
            Using the vxtask command
      4.  
        Using vxnotify to monitor configuration changes
      5. Performing online relayout
        1.  
          Permitted relayout transformations
        2.  
          Specifying a non-default layout
        3.  
          Specifying a plex for relayout
        4.  
          Tagging a relayout operation
        5.  
          Viewing the status of a relayout
        6.  
          Controlling the progress of a relayout
      6. Adding a mirror to a volume
        1.  
          Mirroring all volumes
        2.  
          Mirroring volumes on a VxVM disk
      7.  
        Configuring SmartMove
      8.  
        Removing a mirror
      9.  
        Setting tags on volumes
      10. Managing disk groups
        1. Disk group versions
          1.  
            Upgrading the disk group version
          2.  
            Creating a disk group with an earlier disk group version
        2. Displaying disk group information
          1.  
            Displaying free space in a disk group
        3.  
          Creating a disk group
        4.  
          Removing a disk from a disk group
        5.  
          Deporting a disk group
        6. Importing a disk group
          1.  
            Setting the automatic recovery of volumes
        7.  
          Handling of minor number conflicts
        8. Moving disk groups between systems
          1.  
            Handling errors when importing disks
          2.  
            Reserving minor numbers for disk groups
          3.  
            Compatibility of disk groups between platforms
        9. Importing a disk group containing hardware cloned disks
          1.  
            Considerations when using EMC CLARiiON SNAPSHOT LUNs
          2.  
            Writing a new UDID to a disk
          3.  
            Importing the existing disk group with only the cloned disks
          4.  
            Importing the cloned disks as a new standard disk group
          5.  
            Importing a set of cloned disks with tags
        10.  
          Setting up configuration database copies (metadata) for a disk group
        11.  
          Renaming a disk group
        12. Handling conflicting configuration copies
          1.  
            Example of a serial split brain condition in a cluster
          2.  
            Correcting conflicting configuration information
        13.  
          Disabling a disk group
        14. Destroying a disk group
          1.  
            Recovering a destroyed disk group
        15. Backing up and restoring disk group configuration data
          1.  
            Backing up and restoring Flexible Storage Sharing disk group configuration data
        16.  
          Working with existing ISP disk groups
      11. Managing plexes and subdisks
        1. Reattaching plexes
          1.  
            Automatic plex reattachment
          2.  
            Reattaching a plex manually
        2.  
          Plex synchronization
      12. Decommissioning storage
        1.  
          Removing a volume
        2.  
          Removing a disk from VxVM control
        3.  
          About shredding data
        4.  
          Shredding a VxVM disk
        5.  
          Failed disk shred operation results in a disk with no label
        6. Removing and replacing disks
          1.  
            Replacing a failed or removed disk
    2. Rootability
      1.  
        Root Disk Encapsulation (RDE) is not supported
      2. Encapsulating a disk
        1.  
          Failure of disk encapsulation
        2. Using nopriv disks for encapsulation
          1.  
            Creating a nopriv disk for encapsulation
          2.  
            Creating volumes for other partitions on a nopriv disk
      3.  
        Device name format changes in RHEL 7 environments after encapsulation
      4. Rootability
        1.  
          Restrictions on using rootability with Linux
        2. Sample supported root disk layouts for encapsulation
          1.  
            Example 1: supported root disk layouts for encapsulation
          2.  
            Example 2: supported root disk layouts for encapsulation
          3.  
            Example 3: supported root disk layouts for encapsulation
          4.  
            Example 4: supported root disk layouts for encapsulation
          5.  
            Sample unsupported root disk layouts for encapsulation
          6.  
            Example 1: unsupported root disk layouts for encapsulation
          7.  
            Example 2: unsupported root disk layouts for encapsulation
          8.  
            Example 3: unsupported root disk layouts for encapsulation
          9.  
            Example 4: unsupported root disk layouts for encapsulation
        3.  
          Booting root volumes
        4.  
          Boot-time volume restrictions
        5.  
          Creating redundancy for the root disk
        6.  
          Creating an archived back-up root disk for disaster recovery
        7. Encapsulating and mirroring the root disk
          1.  
            Allocation of METADATA Subdisks During Root Disk Encapsulation
        8.  
          Upgrading the kernel on a root encapsulated system
      5. Administering an encapsulated boot disk
        1.  
          Creating a snapshot of an encapsulated boot disk
      6.  
        Unencapsulating the root disk
    3. Quotas
      1.  
        About Veritas File System quota limits
      2.  
        About quota files on Veritas File System
      3.  
        About Veritas File System quota commands
      4.  
        About quota checking with Veritas File System
      5. Using Veritas File System quotas
        1.  
          Turning on Veritas File System quotas
        2.  
          Turning on Veritas File System quotas at mount time
        3.  
          Editing Veritas File System quotas
        4.  
          Modifying Veritas File System quota time limits
        5.  
          Viewing Veritas File System disk quotas and usage
        6.  
          Displaying blocks owned by users or groups
        7.  
          Turning off Veritas File System quotas
        8.  
          Support for 64-bit Quotas
    4. File Change Log
      1.  
        About Veritas File System File Change Log
      2.  
        About the Veritas File System File Change Log file
      3.  
        Veritas File System File Change Log administrative interface
      4.  
        Veritas File System File Change Log programmatic interface
      5.  
        Summary of Veritas File System File Change Log API functions
  10. Section X. Reference
    1. Appendix A. Reverse path name lookup
      1.  
        About reverse path name lookup
    2. Appendix B. Tunable parameters
      1.  
        About tuning Storage Foundation
      2. Tuning the VxFS file system
        1.  
          Tuning inode table size
        2.  
          Tuning performance optimization of inode allocation
        3.  
          Tuning file system parallel direct I/O
        4.  
          Partitioned directories
        5.  
          Veritas Volume Manager maximum I/O size
        6.  
          Native asynchronous I/O with cloned processes
      3.  
        DMP tunable parameters
      4. Methods to change Dynamic Multi-Pathing tunable parameters
        1.  
          Changing the values of DMP parameters with the vxdmpadm settune command line
        2. About tuning Dynamic Multi-Pathing (DMP) with templates
          1.  
            DMP tuning templates
          2.  
            Example DMP tuning template
          3.  
            Tuning a DMP host with a configuration attribute template
          4.  
            Managing the DMP configuration files
          5.  
            Resetting the DMP tunable parameters and attributes to the default values
          6.  
            DMP tunable parameters and attributes that are supported for templates
      5. Tunable parameters for VxVM
        1.  
          Tunable parameters for core VxVM
        2.  
          Tunable parameters for FlashSnap (FMR)
        3.  
          Tunable parameters for CVM
        4.  
          Tunable parameters for VVR
        5.  
          Tunable parameters for hot-relocation in FSS environments
        6.  
          Points to note when changing the values of the VVR tunables
      6. Methods to change Veritas Volume Manager tunable parameters
        1.  
          Changing the values of the Veritas Volume Manager tunable parameters using the vxtune command line
        2.  
          Changing the value of the Veritas Volume Manager tunable parameters using templates
    3. Appendix C. Command reference
      1.  
        Command completion for Veritas commands
      2.  
        Veritas Volume Manager command reference
      3. Veritas Volume Manager manual pages
        1.  
          Section 1M - administrative commands
        2.  
          Section 4 - file formats
      4.  
        Veritas File System command summary
      5.  
        Veritas File System manual pages
      6.  
        SmartIO command reference

How a snapshot file system works

A snapshot file system is created by mounting an empty disk slice as a snapshot of a currently mounted file system. The bitmap, blockmap and super-block are initialized and then the currently mounted file system is frozen. After the file system to be snapped is frozen, the snapshot is enabled and mounted and the snapped file system is thawed. The snapshot appears as an exact image of the snapped file system at the time the snapshot was made.

See Freezing and thawing a file system.

Initially, the snapshot file system satisfies read requests by finding the data on the snapped file system and returning it to the requesting process. When an inode update or a write changes the data in block n of the snapped file system, the old data is first read and copied to the snapshot before the snapped file system is updated. The bitmap entry for block n is changed from 0 to 1, indicating that the data for block n can be found on the snapshot file system. The blockmap entry for block n is changed from 0 to the block number on the snapshot file system containing the old data.

A subsequent read request for block n on the snapshot file system will be satisfied by checking the bitmap entry for block n and reading the data from the indicated block on the snapshot file system, instead of from block n on the snapped file system. This technique is called copy-on-write. Subsequent writes to block n on the snapped file system do not result in additional copies to the snapshot file system, since the old data only needs to be saved once.

All updates to the snapped file system for inodes, directories, data in files, extent maps, and so forth, are handled in this fashion so that the snapshot can present a consistent view of all file system structures on the snapped file system for the time when the snapshot was created. As data blocks are changed on the snapped file system, the snapshot gradually fills with data copied from the snapped file system.

The amount of disk space required for the snapshot depends on the rate of change of the snapped file system and the amount of time the snapshot is maintained. In the worst case, the snapped file system is completely full and every file is removed and rewritten. The snapshot file system would need enough blocks to hold a copy of every block on the snapped file system, plus additional blocks for the data structures that make up the snapshot file system. This is approximately 101 percent of the size of the snapped file system. Normally, most file systems do not undergo changes at this extreme rate. During periods of low activity, the snapshot should only require two to six percent of the blocks of the snapped file system. During periods of high activity, the snapshot might require 15 percent of the blocks of the snapped file system. These percentages tend to be lower for larger file systems and higher for smaller ones.

Warning:

If a snapshot file system runs out of space for changed data blocks, it is disabled and all further attempts to access it fails. This does not affect the snapped file system.