Virtual machine snapshot or restore

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Virtual machine (instance) snapshot allows you to take consistent snapshot of the volumes attached to a virtual machine. You can create multiple snapshot copies for a single virtual machine. You can also choose to select one or more volumes while creating instance snapshots. These instance snapshots can be further used to restore the virtual machine at any point in time.

This topic explains certain aspects such as prerequisites, use cases, considerations, and limitations for snapshot and restore operations on a virtual machine.

Virtual machine (instance) snapshot is only supported for IBM® Storwize®, PowerMax, and Hitachi storage providers with non replicated volumes.

Virtual machine (instance) snapshot is supported for Pure Storage with single volume.

Snapshot

On the PowerVC user interface, navigate to VM list, select a virtual machine, and then click Snapshot. You can choose to snapshot all volumes associated with the virtual machine, only boot volume, or the boot volume and selected data volumes from the list. The snapshot request for the selected VM or VMs is sent to for admin approvals.

Prerequisites

Before taking the snapshots ensure that entire data is flushed to the disk. If the snapshot is taken on a running virtual machine, then there may be chances of losing content which resides in the filesystem memory and not yet written on the disk. If the volumes has any Oracle database application, ensure all the transactions are committed before performing the instance snapshot.

  • For IBM i, you must perform these steps each time you take a snapshot or clone a virtual machine.
    • Before taking a snapshot or cloning a VM, run 
      CHGASPACT ASPDEV(ASPNAME) OPTION(*SUSPEND) SSPTIMO(timeout_value)
      This command suspends database transactions and Integrated File System (IFS) file change operations for the system and basic auxiliary storage pools (ASPs) or independent ASPs.
    • After taking a snapshot or cloning a VM, run
      CHGASPACT ASPDEV({ASPNAME}) OPTION(*RESUME)
      This command resumes suspended transactions and file operations for the system and basic auxiliary storage pools (ASPs) or independent ASPs.
  • All volumes that are selected for snapshot must have a storage template assigned.
  • All selected volumes must be from the same storage provider.

Supported use cases

PowerVC supports the following snapshot use case scenarios:
  • Take snapshot of a virtual machine with only boot volume selected.
  • Take snapshot of a virtual machine with all volumes (boot and data) selected.
  • Take snapshot of a virtual machine with only data volumes selected.
  • Take multiple snapshots of a single virtual machine, one at a time.
  • Take multiple snapshots of different virtual machines at a time.
  • Attach volume to a virtual machine whose instance snapshot is taken.
  • Take snapshot of a virtual machine that has shared volume.

Considerations

  • During virtual machine snapshot process, virtual machine goes into snapshotting state, so no other operations are allowed.
  • If the virtual machine has instance snapshot, you cannot detach the volume for which snapshot is taken. You must first delete the snapshot, and then detach the volume if required.
  • You cannot unmanage the virtual machine that has instance snapshot. To unmanage the virtual machine from PowerVC, you must first delete all the instance snapshots.
  • Volumes that are selected for instance snapshot must have a valid storage template assigned. Snapshot is not allowed for the volumes with missing storage template.
  • Volume resize is restricted for the volumes that are part of an instance snapshot.

Restore

You can restore the volume snapshots created as a part of virtual machine snapshot operation.

Prerequisites

By default PowerVC warns you to Poweroff the virtual machine while performing the restore. You can also perform the force restore to initiate the restore on the running virtual machine. While performing restore operations on running VM, ensure that the applications are quiesced and no I/O is happening on the volume disks.

Supported use cases

PowerVC supports the following snapshot use case scenarios:
  • Restore all volumes, which are part of virtual machine snapshot.
  • Retry the restore operation if the previous operations failed for any reason.
  • Rollback the virtual machine restore to original volume state in case the snapshot restore fails.

Considerations

  • Before performing the virtual machine restore, PowerVC takes the backup snapshot for all the volumes to be restored. As a result, the virtual machine is rolled back to the original state if any failure happens during restore.
  • Volume restore is not allowed if there are any copy operations that are running on the target volume. PowerVC validates for the copy operations for all volumes before starting restore operation.
  • When virtual machine restore is performed, the virtual machine task status goes into restoring and the volume status is changed to reverting, and no other virtual machine operations are allowed.
  • When restore of a virtual machine fails, virtual machine goes into Error state. User can retry or rollback the virtual machine to original volume state.
  • If restore operation is performed on the shared volume, all virtual machines that are sharing the volume are restored.
  • If restore operation is performed on the shared volume on one virtual machine, user cannot perform the snapshot, restore, clone, or capture on the other virtual machines that use the shared volume.
  • Before performing restore operation on a boot disk, the virtual machine must be moved to Shutoff state.
  • After successful restore retry operation, the VM state might not reset from Error state. Use Reset State feature on the UI to reset VM state.