Veritas™ Volume Manager Administrator's Guide
- Understanding Veritas Volume Manager
- VxVM and the operating system
- How VxVM handles storage management
- Volume layouts in VxVM
- Online relayout
- Volume resynchronization
- Dirty region logging
- Volume snapshots
- FastResync
- Provisioning new usable storage
- Administering disks
- Disk devices
- Discovering and configuring newly added disk devices
- Discovering disks and dynamically adding disk arrays
- How to administer the Device Discovery Layer
- Changing the disk-naming scheme
- Adding a disk to VxVM
- Rootability
- Displaying disk information
- Removing disks
- Removing and replacing disks
- Administering Dynamic Multi-Pathing
- How DMP works
- Administering DMP using vxdmpadm
- Gathering and displaying I/O statistics
- Specifying the I/O policy
- Online dynamic reconfiguration
- Reconfiguring a LUN online that is under DMP control
- Creating and administering disk groups
- About disk groups
- Displaying disk group information
- Creating a disk group
- Importing a disk group
- Moving disk groups between systems
- Handling cloned disks with duplicated identifiers
- Handling conflicting configuration copies
- Reorganizing the contents of disk groups
- Destroying a disk group
- Creating and administering subdisks and plexes
- Displaying plex information
- Reattaching plexes
- Creating volumes
- Types of volume layouts
- Creating a volume
- Using vxassist
- Creating a volume on specific disks
- Creating a mirrored volume
- Creating a striped volume
- Creating a volume using vxmake
- Initializing and starting a volume
- Using rules and persistent attributes to make volume allocation more efficient
- Administering volumes
- Displaying volume information
- Monitoring and controlling tasks
- Reclamation of storage on thin reclamation arrays
- Stopping a volume
- Resizing a volume
- Adding a mirror to a volume
- Preparing a volume for DRL and instant snapshots
- Adding traditional DRL logging to a mirrored volume
- Enabling FastResync on a volume
- Performing online relayout
- Adding a RAID-5 log
- Creating and administering volume sets
- Configuring off-host processing
- Administering hot-relocation
- How hot-relocation works
- Moving relocated subdisks
- Administering cluster functionality (CVM)
- Overview of clustering
- Multiple host failover configurations
- CVM initialization and configuration
- Dirty region logging in cluster environments
- Administering VxVM in cluster environments
- Changing the CVM master manually
- Importing disk groups as shared
- Administering sites and remote mirrors
- About sites and remote mirrors
- Fire drill - testing the configuration
- Changing the site name
- Administering the Remote Mirror configuration
- Failure and recovery scenarios
- Performance monitoring and tuning
- Appendix A. Using Veritas Volume Manager commands
- Appendix B. Configuring Veritas Volume Manager
Specifying ordered allocation of storage to volumes
Ordered allocation gives you complete control of space allocation. It requires that the number of disks that you specify to the vxassist command must match the number of disks that are required to create a volume. The order in which you specify the disks to vxassist is also significant.
If you specify the -o ordered option to vxassist when creating a volume, any storage that you also specify is allocated in the following order:
Concatenate disks.
Form columns.
Form mirrors.
For example, the following command creates a mirrored-stripe volume with 3 columns and 2 mirrors on 6 disks in the disk group, mydg:
# vxassist -b -g mydg -o ordered make mirstrvol 10g \ layout=mirror-stripe ncol=3 mydg01 mydg02 mydg03 mydg04 mydg05 mydg06
This command places columns 1, 2 and 3 of the first mirror on disks mydg01, mydg02 and mydg03 respectively, and columns 1, 2 and 3 of the second mirror on disks mydg04, mydg05 and mydg06 respectively.
Figure: Example of using ordered allocation to create a mirrored-stripe volume shows an example of using ordered allocation to create a mirrored-stripe volume.
For layered volumes, vxassist applies the same rules to allocate storage as for non-layered volumes. For example, the following command creates a striped-mirror volume with 2 columns:
# vxassist -b -g mydg -o ordered make strmirvol 10g \ layout=stripe-mirror ncol=2 mydg01 mydg02 mydg03 mydg04
This command mirrors column 1 across disks mydg01 and mydg03, and column 2 across disks mydg02 and mydg04.
Figure: Example of using ordered allocation to create a striped-mirror volume shows an example of using ordered allocation to create a striped-mirror volume.
Additionally, you can use the col_switch attribute to specify how to concatenate space on the disks into columns. For example, the following command creates a mirrored-stripe volume with 2 columns:
# vxassist -b -g mydg -o ordered make strmir2vol 10g \ layout=mirror-stripe ncol=2 col_switch=3g,2g \ mydg01 mydg02 mydg03 mydg04 mydg05 mydg06 mydg07 mydg08
This command allocates 3 gigabytes from mydg01 and 2 gigabytes from mydg02 to column 1, and 3 gigabytes from mydg03 and 2 gigabytes from mydg04 to column 2. The mirrors of these columns are then similarly formed from disks mydg05 through mydg08.
Figure: Example of using concatenated disk space to create a mirrored-stripe volume shows an example of using concatenated disk space to create a mirrored-stripe volume.
Other storage specification classes for controllers, enclosures, targets and trays can be used with ordered allocation. For example, the following command creates a 3-column mirrored-stripe volume between specified controllers:
# vxassist -b -g mydg -o ordered make mirstr2vol 80g \ layout=mirror-stripe ncol=3 \ ctlr:c1 ctlr:c2 ctlr:c3 ctlr:c4 ctlr:c5 ctlr:c6
This command allocates space for column 1 from disks on controllers c1, for column 2 from disks on controller c2, and so on.
Figure: Example of storage allocation used to create a mirrored-stripe volume across controllers shows an example of using storage allocation to create a mirrored-stripe volume across controllers.
There are other ways in which you can control how vxassist lays out mirrored volumes across controllers.
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