Taking a snapshot

Virtual Storage Platform One SDS Block Virtual Private Storage Administrator Guide
Version
1.15.x
Audience
anonymous
Part Number
MK-24VSP1SDS003-02

Run either of the following commands with the copy-destination volume created in the preparatory step specified.

  • If a snapshot in the Restoring state exists under the copy-source volume, a snapshot cannot be taken.

  • You can take a snapshot only when the copy-destination snapshot is in Prepared state.

  • If the copy-source volume is a snapshot, you can take a snapshot only when the copy-source snapshot is in Normal state.

Note:

  • After a snapshot is taken, a write request for the P-VOL is processed with the CoW (Copy-on-Write) method. In the CoW method, the data existing before a write is performed is copied to the storage pool, and then the write is performed.

  • Immediately after creating a snapshot volume, whenever the data in the P-VOL is updated, the difference data is copied. If many write I/O operations are performed from the host continuously, a large amount of difference data will be copied. This will increase the load on the storage node, causing degradation in IOPS performance of write and read I/O operations. If IOPS performance is degraded, reduce the number of write I/O operations from the host.

CAUTION:

To keep data consistent, stop the host I/O until a snapshot has been taken. If the volume is for the OS system disk, take a snapshot after shutting down the OS. For a data disk volume, forcibly write file cache to disk and stop writing data to the drive (for example, with the sync command and fsfreeze command) or unmount the disk, and then take a snapshot. After a snapshot has been obtained, resume the host I/O operations. The steps for stopping the host I/O operations depend on the OS. Stop the host I/O operations according to the steps for the OS you are using.

  • Required role: VpsStorage

  1. Verify the ID of the volume for which you want to create a snapshot.

    If you want to specify a volume by its name in the CLI, verify the name of the intended volume.

    REST API: GET /v1/objects/volumes

    CLI: volume_list

  2. Obtain a list of S-VOL information by specifying the ID of the copy-source volume, and verify that there is no volume with snapshotStatus of "Restoring". Also, verify the ID of the copy-destination volume and make sure that snapshotStatus is "Prepared".

    If you use the CLI, you can specify a name instead of the ID of the volume.

    REST API: GET /v1/objects/volumes/<id>/snapshot-volumes

    CLI: snapshot_volume_list

    After verification, go to the next step.

  3. Take a snapshot.

    Run either of the following commands with the ID of the copy-source volume specified and "Finalize" specified for the operationType parameter.

    If you want to use the CLI, you can specify the name of the volume instead of its ID. The parameter is operation_type and the specified value is "Finalize".

    REST API: POST /v1/objects/volumes/actions/create-snapshot/invoke

    CLI: volume_create_snapshot

    Verify the job ID which is displayed after the command is run.

  4. Verify the state of the job.

    Run either of the following commands with the job ID specified.

    REST API: GET /v1/objects/jobs/<jobId>

    CLI: job_show

    If the job state is "Succeeded", the job is completed.

  5. Obtain information about replication-destination volumes to verify that the snapshotStatus has changed to "Normal".

    REST API: GET /v1/objects/volumes/<id>

    CLI: volume_show

    After performing step 4, it might take approximately one minute for the snapshot status to change. When you want to verify that the snapshot status has changed, wait for approximately one minute before verification.