InfoScale™ 9.0 Replication Administrator's Guide - AIX

Last Published:
Product(s): InfoScale & Storage Foundation (9.0)
Platform: AIX
  1. Section I. Getting started with Volume Replicator
    1. Introducing Volume Replicator
      1. What is VVR?
        1.  
          Features of VVR
        2.  
          VVR terminology defined
      2.  
        Components of VVR
      3. How the VVR components fit together
        1.  
          VVR at the Primary
        2.  
          VVR at the Secondary
        3.  
          Local host (localhost)
      4.  
        Modes of VVR replication
      5.  
        VCS agents for VVR
      6.  
        Replication configurations with 4K sector-sized disks
    2. Understanding how Volume Replicator works
      1.  
        How VVR processes application writes
      2. How VVR uses kernel buffers for replication
        1.  
          About replication in synchronous mode
        2.  
          Data flow when reading back from the SRL
      3.  
        How data flows in VVR asynchronous mode
      4.  
        About secondary logging enabled asynchronous mode
      5.  
        About bulk transfer with secondary logging
      6.  
        How data flows in VVR asynchronous mode with secondary logging
      7.  
        How data flows in VVR synchronous mode
      8.  
        How data flows in an RDS containing multiple Secondary hosts
      9. Replication in a shared disk group environment
        1.  
          The role of the logowner
        2.  
          How VVR processes a write in a shared disk group
        3.  
          How VVR processes a read in a shared disk group
      10.  
        Assigning a slave node as a logowner
      11.  
        Understanding how VVR logs writes to the SRL
      12.  
        Understanding Storage Checkpoints
      13.  
        Volume sets in VVR
      14.  
        Changing membership of an RVG and a volume set
      15. Using SmartTier with VVR
        1.  
          Best practices for using SmartTier with VVR
      16.  
        Cross-platform Data Sharing in VVR
      17. Understanding the VVR snapshot feature
        1.  
          About snapshots of RVGs containing volume sets
        2.  
          About the traditional snapshot feature
        3. About the instant snapshot feature
          1.  
            About instant full snapshots
          2.  
            About Instant space-optimized snapshots
          3.  
            About Instant plex-breakoff snapshots
        4.  
          How VVR creates instant space-optimized snapshots
        5.  
          Comparing VVR snapshot methods based on different features
      18. About VVR compression
        1.  
          General functionality considerations for VVR compression
    3. Planning and configuring replication
      1.  
        Introduction to planning and configuring replication
      2. Before you begin configuring
        1.  
          Understanding business needs
        2.  
          Understanding application characteristics
      3. Choosing the mode of volume replication
        1.  
          Asynchronous mode replication considerations
        2. Synchronous mode replication considerations
          1.  
            Synchronous mode considerations when the synchronous attribute is set to fail
        3.  
          Asynchronous volume replication versus synchronous volume replication
      4.  
        Choosing latency and SRL protection
      5. Planning the network
        1. Choosing the network bandwidth
          1.  
            Bandwidth of the available network connection
          2.  
            How network performance depends on the mode of replication
        2.  
          Choosing the network protocol
        3.  
          Choosing the network ports used by VVR
        4.  
          Configuring VVR in a firewall environment
        5.  
          Choosing the packet size
        6.  
          Choosing the network maximum transmission unit
      6. Sizing the SRL
        1.  
          Peak usage constraint for sizing the SRL
        2.  
          Synchronization period constraint for sizing the SRL
        3.  
          Secondary backup constraint for sizing the SRL
        4.  
          Secondary downtime constraint for sizing the SRL
        5.  
          Additional factors for sizing the SRL
        6.  
          Example - Calculating SRL size for a VVR configuration
      7.  
        Choosing the type of DCM logging
      8.  
        Best practices for setting up replication
      9.  
        How the agents for hybrid applications work
      10.  
        Pre-requisites to enable data over wire encryption
      11.  
        Enabling Data Change Object (DCO) for SRL Volumes
    4. Understanding replication settings for a Secondary
      1.  
        About replication settings for a Secondary
      2. Modes of VVR replication
        1.  
          About asynchronous volume replication
        2.  
          About synchronous volume replication
        3.  
          About the synchronous attribute
      3. Protecting against SRL overflow
        1.  
          About the srlprot attribute
      4. Setting up latency protection
        1. About the latencyprot attribute
          1.  
            About Latency protection when Primary and Secondary are connected
          2.  
            About Latency protection when Primary and Secondary are disconnected
      5.  
        Controlling the network bandwidth used for replication
      6. Choosing the VVR compression mode
        1.  
          Enabling compression
        2.  
          Disabling compression
    5. Configuring VVR in a VCS environment
      1.  
        Overview of how to configure VVR in a VCS environment
      2. Using the primary-elect feature to choose the primary site after a site disaster or network disruption
        1.  
          Application availability in the case of a network disruption using the primary-elect feature
        2.  
          Configuring VCS global clustering so you can choose the Primary site
        3. Choosing the Primary site after a site disaster or network disruption
          1.  
            Example - Choosing the original Primary as the Primary going forward
          2.  
            Example - Choosing the original Secondary as the Primary going forward
        4. Troubleshooting the primary-elect feature
          1.  
            Troubleshooting failures in the RVGPrimary online agent function
          2.  
            Troubleshooting failures in VVR ElectPrimary command
      3. Requirements for configuring VVR in a VCS environment
        1.  
          Best practices for setting up VVR agents
      4.  
        Generic VVR setup in a VCS environment
      5.  
        Example VVR configuration in a VCS environment
      6.  
        Example RVG configuration for a failover application
      7.  
        Example RVG configuration for a parallel application
      8. Example setting up VVR in a VCS environment
        1.  
          Setting up the VVR configuration
        2.  
          Verifying the VVR replication state
        3. Configuring the VVR agents for failover applications
          1.  
            Configuring the agents when VCS is running
          2.  
            Configuring the agents when VCS is stopped
        4.  
          Configuring the VVR agents for parallel applications
      9. Configuring the agents for a bunker replication configuration
        1. VCS configuration for a bunker using the STORAGE protocol
          1. Sample configuration file for VCS agents in a bunker replication environment
            1.  
              Sample configuration file (failover application)
        2.  
          VCS configuration for a bunker using IP
        3. How the RVGPrimary works in a bunker setup
          1.  
            About bunker SRL overflow
          2.  
            About global clustering with bunker replay
      10.  
        Administering VCS service groups
  2. Section II. Setting up and administering VVR
    1. Setting up replication
      1.  
        About configuring VVR replication
      2.  
        Enabling security certificate
      3.  
        Setting up the certificate authority (CA) certificates in /etc/vx/vvr/cacert.pem
      4. Creating a Replicated Data Set
        1. Creating a Primary RVG of an RDS
          1.  
            Prerequisites for creating a Primary RVG of an RDS
          2.  
            Example - Creating a Primary RVG containing a data volume
          3.  
            Example - Creating a Primary RVG containing a volume set
        2. Adding a Secondary to an RDS
          1.  
            Best practices for adding a Secondary to an RDS
          2.  
            Prerequisites for adding a Secondary to an RDS
        3. Changing the replication settings for a Secondary
          1. Setting the mode of replication for a Secondary
            1.  
              Example - Setting the mode of replication to asynchronous for an RDS
            2.  
              Example - Setting the mode of replication to synchronous for an RDS
          2.  
            Setting the latency protection for a Secondary
          3.  
            Setting the SRL overflow protection for a Secondary
          4.  
            Setting the network transport protocol for a Secondary
          5. Setting the packet size for a Secondary
            1.  
              Example - Setting the packet size between the Primary and Secondary
          6. Setting the bandwidth limit for a Secondary
            1.  
              Example: Limiting network bandwidth between the Primary and the Secondary
            2.  
              Example: Disabling Bandwidth Throttling between the Primary and the Secondary
            3.  
              Example: Limiting network bandwidth used by VVR when using full synchronization
      5. Synchronizing the Secondary and starting replication
        1. Methods to synchronize the Secondary
          1.  
            Using the network to synchronize the Secondary
          2.  
            Using block-level tape backup to synchronize the Secondary
          3.  
            Moving disks physically to synchronize the Secondary
        2. Using the automatic synchronization feature
          1.  
            Notes on using automatic synchronization
        3.  
          Example for setting up replication using automatic synchronization
        4.  
          About SmartMove for VVR
        5.  
          About thin storage reclamation and VVR
        6.  
          Determining if a thin reclamation array needs reclamation
      6. Starting replication when the data volumes are zero initialized
        1.  
          Example: Starting replication when the data volumes are zero initialized
      7.  
        Starting replication over the wire when data volumes are encrypted
      8.  
        Setting up replication with different sector-sized disks
    2. Displaying configuration information
      1. Displaying RVG and RDS information
        1.  
          Displaying RDS information
        2.  
          Displaying individual RVG information
        3.  
          Interpreting RVG flag settings
      2. Displaying information about data volumes and volume sets
        1.  
          Displaying data volumes in a Replicated Data Set
        2.  
          Displaying a list of data volumes
        3.  
          Displaying information about all failed data volumes
        4.  
          Displaying an individual data volume
        5.  
          Displaying a volume set
      3. Displaying information about Secondaries
        1.  
          Displaying consolidated replication status
        2.  
          Displaying a list of RLINKs
        3. Displaying a specific RLINK
          1.  
            Interpreting RLINK flag settings
        4.  
          Displaying the status of a Secondary
      4.  
        Displaying a list of Storage Checkpoints
      5. Displaying statistics with the vrstat display commands
        1.  
          Displaying the consolidated statistics
        2.  
          Displaying the RLINK information for all the hosts in the RDS
        3.  
          Displaying information about all the data volumes for all the hosts in the RDS
        4.  
          Displaying information about the SRL volumes for all the hosts in the RDS
        5.  
          Displaying information about the memory tunable parameters for all the hosts in the RDS
        6.  
          Determining VVR network bandwidth usage and compression ratio
      6. Collecting consolidated statistics of the VVR components
        1. Understanding how VVR stores the statistics
          1.  
            About the VVR statistics Messages heading
          2.  
            About the VVR statistics Errors heading
          3.  
            About the VVR statistics Flow control heading
      7. Displaying network performance data
        1.  
          Displaying extended replication statistics
        2. Identifying the most up-to-date Secondary
          1.  
            Example - to determine the most up-to-date Secondary
          2.  
            Example - to determine the status of the Secondary
      8.  
        VVR event notification
    3. Administering Volume Replicator
      1. Administering data volumes
        1. Associating a volume to a Replicated Data Set
          1.  
            Example - Associating an existing volume to an RDS
          2. Verifying the data on the Primary and Secondary volumes
            1.  
              Example - Verifying the differences between remote volumes on a host
          3. Synchronizing volumes on the local host and remote hosts
            1.  
              Synchronizing volumes using full synchronization
            2.  
              Example - Full synchronization of volumes on local and remote hosts
            3.  
              Synchronizing volumes using difference-based synchronization
        2. Associating a volume set to an RDS
          1.  
            Example:
          2.  
            Example
        3.  
          Associating a Data Change Map to a data volume in DCO
        4. Associating a Data Change Map to a data volume as a log plex
          1.  
            Determining the region size
        5. Resizing a data volume in a Replicated Data Set
          1.  
            Important notes on resizing a data volume in a Replicated Data Set
          2.  
            Prerequisites for resizing a data volume in an RDS
        6.  
          Renaming a data volume in a Replicated Data Set
        7.  
          Dissociating a data volume from its Replicated Data Set
        8.  
          Mapping the name of a Secondary data volume to a differently named Primary data volume
        9.  
          Mapping disk groups
      2. Administering the SRL
        1.  
          Protecting from SRL overflow
        2. Incrementally synchronizing the Secondary after SRL overflow
          1.  
            SRL overflow protection with DCM - flags and definitions
          2.  
            Prerequisite for incrementally synchronizing the Secondary
          3.  
            Breaking off mirrors before incremental synchronization
          4.  
            Example - Resynchronizing the Secondary using break off mirrors
          5.  
            Example - Recreating volumes if a disaster occurs during resynchronization
          6.  
            Notes on using incremental synchronization on SRL overflow
        3.  
          Changing the size of the SRL on the Primary and the Secondary
        4.  
          Decreasing the size of the SRL on the Primary
      3. Administering replication
        1.  
          Changing the replication settings
        2.  
          Pausing and resuming replication to a Secondary
        3.  
          Stopping replication to a Secondary
        4. Changing the IP addresses used for replication
          1.  
            Prerequisites for changing the IP addresses used for replication
          2.  
            Example for changing IP addresses to a different IPv4 network
          3.  
            Example for changing IP addresses to a different IPv6 network
        5. Changing the network ports used for replication
          1.  
            Port numbers used by VVR
          2. Displaying and changing the ports used by VVR
            1.  
              Displaying the port used for heartbeats
            2.  
              Example - Changing the replication heartbeat port
            3.  
              Displaying the port used by vradmind
            4.  
              Displaying the port used by in.vxrsyncd
            5.  
              Displaying the ports used to replicate data using UDP
            6.  
              Displaying the ports used to replicate data using TCP
      4. Administering the Replicated Data Set
        1.  
          Removing a Secondary RVG from a Replicated Data Set
        2. Removing a Primary RVG from a Replicated Data Set
          1.  
            Prerequisite for deleting a Primary RVG from a Replicated Data Set
          2.  
            Example - Removing a Primary RVG from an RDS when the application is inactive
          3.  
            Example - Removing a Primary RVG from an RDS when the application is active
      5. Administering Storage Checkpoints
        1.  
          Creating Storage Checkpoints
        2.  
          Ending Storage Checkpoints
        3.  
          Viewing Storage Checkpoints
        4.  
          Deleting Storage Checkpoints
      6. Creating RVG snapshots
        1. Using the instant snapshot feature
          1.  
            Snapshot naming conventions
        2. About instant full snapshots
          1.  
            Prerequisites for creating instant full snapshots
          2.  
            Creating snapshot volumes for data volumes in an RVG
          3. Preparing the volumes prior to using the instant snapshot feature
            1.  
              Upgrading the disk group for an instant snapshot
            2.  
              Preparing volumes for an instant snapshot
          4.  
            Freezing or pausing replication prior to taking a snapshot
          5. Creating instant full snapshots
            1.  
              Example - Specifying a prefix for snapshots of each data volume in an RVG
            2.  
              Example - Creating an instant full snpashot for an RVG
          6.  
            Unfreezing or resuming replication after taking a snapshot
        3. About instant space-optimized snapshots
          1.  
            Preparing the RVG volumes for snapshot operation
          2.  
            Creating the cache object for instant space-optimized snapshots
          3.  
            Freezing or pausing replication prior to creating an instant space-optimized snapshot
          4. Creating instant space-optimized snapshots
            1.  
              Example: Creating instant space-optimized snapshots
          5.  
            Unfreezing or resuming replication after taking an instant space-optimized snapshot
        4. About instant plex-breakoff snapshots
          1.  
            Preparing the RVG volumes for snapshot operation
          2.  
            Creating snapshot plexes for data volumes in an RVG
          3.  
            Freezing or pausing replication prior to creating a plex-breakoff snapshot
          4. Creating instant plex-breakoff snapshots
            1.  
              Prerequisites for creating instant plex-breakoff snapshots
            2.  
              Example - Creating an instant plex-breakoff snapshot
          5.  
            Unfreezing or resuming replication after taking a plex-breakoff snapshot
        5. Administering snapshots
          1.  
            Refreshing snapshots
          2.  
            Reattaching the snapshot plexes to the data volumes (snapback)
          3. Restoring data from the snapshots
            1.  
              Rules for restoring volumes
          4.  
            Displaying the snapshot information
          5.  
            Destroying the snapshots
        6. Using the traditional snapshot feature
          1.  
            Creating snapshot plexes for data volumes in an RVG
          2.  
            Freezing or pausing replication
          3.  
            Taking a snapshot
          4.  
            Unfreezing or resuming replication
          5.  
            Performing the required operations on the snapshot
          6.  
            Reattaching the snapshot plexes to the data volumes (Snapback)
          7. Using snapback with resyncfromreplica option
            1.  
              Using resyncfromreplica option to recover from logical corruption of data
            2.  
              Using resyncfromreplica to recover failed Secondary data volumes
        7. Using Veritas Volume Manager FastResync
          1.  
            Enabling FastResync
      7. Verifying the DR readiness of a VVR setup
        1.  
          Performing a failover
        2. Performing a fire drill
          1.  
            Automating the fire drill procedure
        3. Verifying the data on the Secondary
          1.  
            Performing online data verification
          2. Performing offline data verification
            1.  
              Prerequisites for using the vradmin -verify syncrvg command
      8. Backing up the Secondary
        1.  
          Restoring the Secondary RLINK from a Secondary Storage Checkpoint
        2. Restoring the Secondary from online backup
          1.  
            Restoring from Secondary Storage Checkpoints
          2.  
            Restoring a Secondary RLINK
    4. Using VVR for off-host processing
      1.  
        About using VVR for off-host processing
      2.  
        What is off-host processing?
      3. In-Band Control Messaging overview
        1. How to use the data on the Secondary
          1.  
            Using snapshots of Secondary data volumes
      4.  
        In-BandControl Messaging explained
      5. Performing off-host processing tasks
        1.  
          Tasks to perform for off-host processing
        2. Using the IBC messaging command vradmin ibc
          1. Prerequisites for using vradmin ibc command
            1.  
              Example - Creating a snapshot on the Secondary using the vradmin ibc command
          2. Understanding the scripts used for the vradmin ibc command
            1.  
              Location of the scripts used for the vradmin ibc command
          3.  
            Sample vradmin ibc command scripts
      6. Examples of off-host processing
        1.  
          Example - Decision support using the snapshot feature and the vradmin ibc command
        2.  
          Example - Backing up using the snapshot feature and the vradmin ibc command
        3.  
          Example - Performing block-level backup of the Secondary data using the vradmin ibc command
    5. Transferring the Primary role
      1.  
        About transferring the Primary role
      2. Migrating the Primary
        1.  
          Prerequisites for migrating the Primary
        2.  
          Important notes for migrating the Primary role
        3.  
          Example - Migrating from a healthy Primary
        4.  
          Example - Migrating the Primary role in a setup with multiple Secondaries
      3. About taking over from an original Primary
        1. Important notes about taking over from an original Primary
          1. About fast failback
            1.  
              Taking over from an original Primary
        2.  
          Example -Taking over from an original Primary
        3.  
          Example - Taking over from an original Primary in a setup with multiple Secondaries
      4. Failing back to the original Primary
        1.  
          Fast failback versus difference-based synchronization
        2. Failing back using fast failback synchronization
          1.  
            Example - Failing back to the original Primary using fast failback
          2.  
            Example - Failing back to the original Primary using fast failback in a multiple Secondaries setup
        3. Failing back using difference-based synchronization
          1.  
            Converting an original Primary to a Secondary
          2.  
            Example - Failing back to the original Primary using difference-based synchronization
          3.  
            Example - Failing back to the original Primary using difference-based synchronization in a multiple Secondaries setup
      5.  
        About choosing the Primary site after a site disaster or network disruption
      6.  
        Application availability in the case of a network disruption
      7.  
        Configuring VCS global clustering so you can choose the Primary site
      8. Choosing the Primary site after a site disaster or network disruption
        1.  
          Example - Choosing the original Primary as the Primary going forward
        2.  
          Example - Choosing the original Secondary as the Primary going forward
      9. Troubleshooting the primary-elect feature
        1.  
          Troubleshooting failures in the RVGPrimary online agent function
        2.  
          Troubleshooting failures in VVR ElectPrimary command
      10.  
        Primary-elect configuration limitations
    6. Replication using a bunker site
      1. Introduction to replication using a bunker site
        1.  
          About replication using a bunker site during normal operations
        2.  
          How the bunker site is used for disaster recovery
        3.  
          Best practices for setting up replication using a bunker site
      2.  
        Sample bunker configuration
      3. Setting up replication using a bunker site
        1.  
          Requirements for replication using a bunker site
        2.  
          Best practices for setting up replication using a bunker site
        3.  
          Adding a bunker to an RDS
        4.  
          Changing replication settings for the bunker Secondary
        5.  
          Starting replication to the bunker
        6.  
          Reinitializing the bunker
      4.  
        Administering replication using a bunker site
      5. Using a bunker for disaster recovery
        1. Updating the Secondary from the bunker
          1.  
            Updating the Secondary from the bunker automatically
          2.  
            Updating the Secondary from the bunker manually
        2. Restoring the original Primary in a bunker setup
          1.  
            Recovering the original Primary during bunker replay
          2.  
            Failing back to the original Primary
          3.  
            Restoring the bunker setup after failback to original Primary
      6. Replication using a bunker site in a VCS environment
        1. Automating local cluster failover for a bunker
          1.  
            Using the StorageHostIds attribute
        2.  
          About bunker replay in a VCS environment
      7.  
        Removing a bunker
      8.  
        About bunker commands
    7. Configuring and administering VVR using System Management Interface Tool
      1.  
        About SMIT for VVR
      2. Accessing Volume Replicator interface in SMIT
        1.  
          Configure Replicated Data Set tasks using SMIT
        2.  
          Replication tasks using SMIT
        3.  
          Change/Show VxVM tunables using SMIT
        4.  
          SMIT screen conventions
      3. Setting up a simple Volume Replicator configuration using SMIT
        1.  
          Creating data volumes and the SRL
        2.  
          Creating the Primary RVG for an RDS using SMIT
        3.  
          Adding a Secondary to the RDS using SMIT
        4.  
          Displaying and configuring RLINK attributes using SMIT
        5. Starting replication using SMIT
          1.  
            Using autosync attach to start replication
          2.  
            Using checkpoint attach to start replication
          3.  
            Using force attach to start replication
      4. Displaying configuration information using SMIT
        1.  
          Displaying the attributes of an RLINK using SMIT
        2.  
          Displaying the attributes of an RVG using SMIT
        3.  
          Displaying the attributes of an RDS using SMIT
      5. Administering Volume Replicator using SMIT
        1.  
          Pausing replication to a Secondary using SMIT
        2.  
          Resuming replication to a Secondary using SMIT
        3.  
          Resynchronizing a Secondary using SMIT
        4.  
          Taking traditional snapshot of data volumes of an RVG using SMIT
        5. Taking instant snapshot of data volumes of an RVG using SMIT
          1.  
            Accessing the SMIT instant snapshot menu
          2.  
            Taking an instant full snapshot using SMIT
          3.  
            Taking an instant space-optimized snapshot using SMIT
          4.  
            Taking an instant plex-breakoff snapshot using SMIT
        6.  
          Snapback of data volumes of an RVG using SMIT
        7. Associating a volume to a Replicated Data Set using SMIT
          1.  
            Prerequisites for associating a volume to an RDS
        8.  
          Dissociating a data volume from a Replicated Data Set using SMIT
        9.  
          Removing a Secondary from a Replicated Data Set using SMIT
        10.  
          Removing a Primary from an RDS using SMIT
        11.  
          Stopping replication to a Secondary using SMIT
        12. Transferring the Primary role using SMIT
          1.  
            Accessing the SMIT transfer role menu
          2.  
            Migrating the Primary and Secondary roles using SMIT
          3.  
            Taking over from a failed Primary using SMIT
          4.  
            Converting the original or failed Primary to a Secondary using SMIT
    8. Troubleshooting VVR
      1.  
        Recovery from RLINK connect problems
      2. Recovery from configuration errors
        1. Errors during an RLINK attach
          1.  
            Data volume errors during an RLINK attach
          2.  
            Volume set errors during an RLINK attach
        2. Errors during modification of an RVG
          1.  
            Missing data volume error during modifcation of an RVG
          2.  
            Data volume mismatch error during modification of an RVG
          3.  
            Data volume name mismatch error during modification of an RVG
          4. Volume set configuration errors during modification of an RVG
            1.  
              Volume set name mismatch error
            2.  
              Volume index mismatch error
            3.  
              Component volume mismatch error
      3. Recovery on the Primary or Secondary
        1.  
          About recovery from a Primary-host crash
        2. Recovering from Primary data volume error
          1.  
            Example - Recovery with detached RLINKs
          2.  
            Example - Recovery with minimal repair
          3.  
            Example - Recovery by migrating the primary
          4.  
            Example - Recovery from temporary I/O error
        3. Primary SRL volume error cleanup and restart
          1.  
            About RVG PASSTHRU mode
        4.  
          Primary SRL volume error at reboot
        5.  
          Primary SRL volume overflow recovery
        6. Primary SRL header error cleanup and recovery
          1.  
            Recovering from SRL header error
        7. Secondary data volume error cleanup and recovery
          1.  
            Recovery using a Secondary Storage Checkpoint
          2.  
            Cleanup using a Primary Storage Checkpoint
        8.  
          Secondary SRL volume error cleanup and recovery
        9.  
          Secondary SRL header error cleanup and recovery
        10.  
          Secondary SRL header error at reboot
    9. Tuning replication performance
      1.  
        Overview of replication tuning
      2. SRL layout
        1.  
          How SRL affects performance
        2.  
          Striping the SRL
        3.  
          Choosing disks for the SRL
        4.  
          Mirroring the SRL
      3. Tuning Volume Replicator
        1. VVR buffer space
          1.  
            Write buffer space on the Primary
          2.  
            Readback buffer space on the Primary
          3.  
            Buffer space on the Secondary
          4.  
            Tunable parameters for the VVR buffer spaces
          5.  
            Tunable parameters for the write buffer space on the Primary in a private disk group
          6.  
            Tunable parameter for the readback buffer space
          7.  
            Tunable parameters for the buffer space on the Primary in a shared disk group
          8.  
            Tunable parameters for the buffer space on the Secondary
        2.  
          DCM replay block size
        3.  
          Heartbeat timeout
        4.  
          Memory chunk size
        5.  
          UDP replication tuning
        6.  
          Tuning the number of TCP connections
        7.  
          Message slots on the Secondary
        8.  
          VVR and network address translation firewall
        9. Tuning VVR compression
          1.  
            Tunable parameter for enabling compression
          2.  
            Tunable parameter for setting compression threads
          3.  
            Tuning considerations for VVR compression
  3. Section III. Analyzing your environment with Volume Replicator Advisor
    1. Introducing Volume Replicator Advisor (VRAdvisor)
      1.  
        Audience
      2.  
        Related Veritas InfoScale documents
      3.  
        Overview of VRAdvisor
      4. How VRAdvisor works
        1.  
          Data collection
        2.  
          Data analysis
        3.  
          What-if analysis
    2. Collecting the sample of data
      1. About collecting the sample of data
        1.  
          Best practices for collecting the sample of data
      2. Collecting the sample of data on UNIX
        1.  
          Prerequisite for collecting the sample of data
        2.  
          Supported locales
        3. Collecting data using the VRAdvisor wizard
          1.  
            Specifying the data to be collected
        4.  
          Collecting data using the vxstat command
        5. Collecting data using the data collection script
          1.  
            Files for the collected data
        6. Examples of collecting data with the data collection script
          1.  
            Example 1
          2.  
            Example 2
          3.  
            Example 3
          4.  
            Example 4
          5.  
            Example 5
      3. Collecting the sample of data on Windows
        1.  
          Prerequisite for collecting the sample of data
        2.  
          Collecting the sample of data using the VRAdvisor wizard
        3.  
          Collecting the sample of data using the diskStats command
    3. Analyzing the sample of data
      1. About analyzing the sample of data
        1.  
          Prerequisites for analyzing the sample of data
      2.  
        Launching the VRAdvisor wizard
      3. Analyzing the collected data
        1. Specifying the data for analysis
          1.  
            Specifying the location of the data files
          2.  
            Selecting the data files to be analyzed
          3.  
            Specifying block size and collection interval for the data files
          4.  
            Selecting volumes or disks for analysis
        2. Specifying the parameters for analysis
          1.  
            Specifying the network parameters for analysis
          2.  
            Specify the RVG-specific parameters
          3.  
            Summary of inputs
      4. Understanding the results of the analysis
        1. Viewing the analysis results
          1.  
            Analysis graph
          2.  
            Analysis results
        2. Recalculating the analysis results
          1.  
            Applying different parameters to the existing sample of data
          2.  
            Performing What-if analysis
          3.  
            Calculating the SRL Size for a specified Network Bandwidth and Outage
          4.  
            Calculating the Network Bandwidth for data loss specified in bytes
          5.  
            Calculating the Network Bandwidth for data loss specified in time duration
          6.  
            Calculating the Network Bandwidth for Bunker and RTO
          7.  
            Changing the value ranges on the slider bar
        3.  
          Recording and viewing the results
    4. Installing Volume Replicator Advisor (VRAdvisor)
      1.  
        VRAdvisor System requirements
      2. Installing VRAdvisor on Solaris
        1.  
          Uninstalling VRAdvisor on Solaris
      3. Installing VRAdvisor on Windows
        1.  
          Uninstalling VRAdvisor on Windows
  4. Section IV. VVR reference
    1. Appendix A. VVR command reference
      1.  
        VVR command reference
    2. Appendix B. Using the In-band Control Messaging utility vxibc and the IBC programming API
      1.  
        About the IBC messaging utility vxibc
      2.  
        In-band Control Messaging overview
      3. Using the IBC messaging command-line utility
        1.  
          Registering an application name
        2.  
          Displaying the registered application name for an RVG
        3.  
          Receiving an IBC message
        4.  
          Sending an IBC message
        5.  
          Unfreezing the Secondary RVG
        6.  
          Unregistering an application name
        7.  
          Receiving and processing an IBC message using a single command
        8.  
          Sending and processing an IBC message using a single command
      4. Examples - Off-host processing
        1.  
          Example 1 - Decision support using the traditional snapshot feature and the vxibc utility
        2.  
          Example 2 - Backing up using the snapshot feature and the vxibc utility
        3.  
          Example 3 - Trial failover using the snapshot feature
        4.  
          Example 4 - Decision support using the instant full snapshot feature and the vxibc utility
      5. In-band Control Messaging API
        1. IOCTL commands
          1.  
            RV_IBC_REGISTER
          2.  
            RV_IBC_SEND
          3.  
            RV_IBC_RECEIVE
          4.  
            RV_IBC_UNFREEZE
          5.  
            RV_IBC_UNREGISTER
          6.  
            RV_IBC_STATUS
        2.  
          Using the IBC API
    3. Appendix C. Volume Replicator object states
      1. Volume Replicator Kernel State
        1.  
          RVG KSTATEs
        2.  
          RLINK KSTATEs
      2. Volume Replicator utility states
        1.  
          RVG utility states
        2.  
          RLINK utility states
        3.  
          Inactive RLINKs
        4.  
          STALE RLINK state
        5.  
          FAIL RLINK state
        6.  
          Inconsistent RLINKs
        7.  
          Pausing, resuming, and restoring RLINK states
    4. Appendix D. Alternate methods for synchronizing the Secondary
      1. Using the full synchronization feature
        1.  
          Example - Synchronizing the Secondary using full synchronization with Storage Checkpoint
      2. Using block-level backup and Storage Checkpoint
        1.  
          Example - Synchronizing the Secondary using block-level backup
      3.  
        Using the Disk Group Split and Join feature
      4. Using difference-based synchronization
        1.  
          Example - synchronizing the Secondary based on differences
      5. Examples for setting up a simple Volume Replicator configuration
        1.  
          Creating a Replicated Data Set for the examples
        2.  
          Example for setting up replication using full synchronization
        3.  
          Example for setting up replication using block-level backup and checkpointing
        4.  
          Example for setting up replication using Disk Group Split and Join
        5.  
          Example for setting up replication using differences-based synchronization
        6.  
          Example for setting up replication when data volumes are initialized with zeroes
    5. Appendix E. Migrating VVR from IPv4 to IPv6
      1. Migrating VVR to support IPv6 or dual stack
        1.  
          Limitation
        2.  
          Probable VVR configurations and failover considerations
      2.  
        Overview of VVR migration from IPv4 to IPv6
      3. About migrating to IPv6 when VCS global clustering and VVR agents are not configured
        1.  
          Understanding the current IPv4 configuration when VCS global clustering and VVR agents are not configured
        2.  
          Migration prerequisites when VCS global clustering and VVR agents are not configured
        3. Migrating to IPv6 when VCS global clustering and VVR agents are not configured
          1.  
            Modifying the failover service group used for replication to IPv6
          2.  
            Migrating the VVR links from IPv4 to IPv6 when VCS global clustering and VVR agents are not configured
          3.  
            Removing the IPv4 resources from the VCS configuration when VCS global clustering and VVR agents are not configured
      4. About migrating to IPv6 when VCS global clustering and VVR agents are configured
        1.  
          Understanding the current IPv4 configuration when VCS global clustering and VVR agents are configured
        2.  
          Migration prerequisites when VCS global clustering and VVR agents are configured
        3.  
          Migrating to IPv6 when VCS global clustering and VVR agents are configured
        4.  
          Migrating the VCS global clustering service group to IPv6 when VCS global clustering and VVR agents are configured
        5.  
          Adding IP and NIC resources for IPv6 addresses in the RVG agent group when VCS global clustering and VVR agents are configured
        6.  
          Migrating VVR RLINKs from IPv4 to IPv6 when VCS global clustering and VVR agents are configured
        7.  
          Removing the IPv4 resources from the VCS configuration when VCS global clustering and VVR agents are configured
      5. About migrating to IPv6 when VCS global clustering and VVR agents are configured in the presence of a bunker
        1.  
          Understanding the current IPv4 configuration when VCS global clustering and VVR agents are configured in the presence of a bunker
        2.  
          Migration prerequisites when VCS global clustering and VVR agents are configured in the presence of a bunker
        3. Migrating to IPv6 when VCS global clustering and VVR agents are configured in the presence of a bunker
          1.  
            Migrating the VCS global clustering service group to IPv6 when VCS global clustering and VVR agents are configured in the presence of a bunker
          2.  
            Adding the IP and NIC resources for IPv6 addresses in the RVG agent group when VCS global clustering and VVR agents are configured in the presence of a bunker
          3.  
            Migrating VVR RLINKs from IPv4 to IPv6 when VCS global clustering and VVR agents are configured in the presence of a bunker
          4.  
            Removing the IPv4 resources from the VCS configuration when VCS global clustering and VVR agents are configured in the presence of a bunker
    6. Appendix F. Sample main.cf files
      1.  
        Globally clustered VCS and VVR main.cf

Synchronous mode replication considerations

Synchronous mode has the advantage that all writes are guaranteed to reach the Secondary before completing. For some businesses, this may simply be a requirement that cannot be circumvented - in this case, performance is not a factor in the decision. For applications where the choice is not so clear, however, this section discusses some of the performance implications of choosing synchronous operations.

All write requests first result in a write to the SRL.

It is only after this write completes that data is sent to the Secondary. Because synchronous mode requires that the data reach the Secondary and be acknowledged before the write completes, this makes the latency for a write equal to:

SRL latency + Network round trip latency

Thus, synchronous mode can significantly decrease application performance by adding the network round trip to the latency of each write request.

If synchronous mode is to be used, another factor to consider is that if the synchronous attribute is set to fail, synchronous mode throttles incoming write request while catching up from a Storage Checkpoint. this means that if a Secondary takes ten hours to catch up, any application waiting for writes to complete will hang for ten hours if the Secondary is replicating in this mode. For all practical purposes, it is necessary to either shut down the application or temporarily set the mode of replication to asynchronous or set the synchronous attribute to override until the Secondary catches up after a Storage Checkpoint.

If you choose synchronous mode, you must consider what VVR should do if there is a network interruption. In synchronous mode, the synchronous attribute enables you to specify what action is taken when the Secondary is unreachable. The synchronous attribute can be set to override or fail. When the synchronous attribute is set to override, synchronous mode converts to asynchronous during a temporary outage. In this case, after the outage passes and the Secondary catches up, replication reverts to synchronous.

When the synchronous attribute is set to fail, the application receives a failure for writes issued while the Secondary is unreachable. The application is likely to fail or become unavailable, and hence this setting must be chosen only if such a failure is preferable to the Secondary being out of date.

We recommend setting the synchronous attribute to override, as this behavior is suitable for most applications. Setting the synchronous attribute to fail is suitable only for a special class of applications that cannot have even a single write difference between the Primary and Secondary data volumes. In other words, this mode of operation must be used only if you want an application write to fail if the write cannot be replicated immediately. It is imperative that the network connection between hosts using this option must be highly reliable to avert unnecessary application downtime as network outage could cause an application outage.

More Information

Figure: Data flow with multiple Secondary hosts