When you create a
Important:
- The snapshot repository virtual disk's failure policy determines what happens when the snapshot repository virtual disk becomes full (that is, all of its capacity has been used). The failure policy can be set to either fail the snapshot (default setting) or fail incoming I/O to the snapshot's source virtual disk.
- Do not ignore the snapshot repository virtual disk "threshold exceeded" notification. This is the last and only warning you will receive before the snapshot repository virtual disk becomes full. You have the option of increasing the capacity of the snapshot repository virtual disk or increasing the snapshot repository virtual disk threshold capacity warning level. Increasing the warning threshold reduces the time you have to respond the next time you receive a threshold exceeded notification.
- If a snapshot virtual disk or snapshot repository virtual disk is displayed as a
, the has detected physical disks associated with the snapshot or snapshot repository virtual disk are no longer accessible. Missing virtual disks, in most cases, are recoverable. For more information, see Learn About Missing Virtual Disks. - When monitoring a snapshot virtual disk for performance, you will not receive a cache hit percentage, because there is no physical cache on the snapshot. (The physical cache exists on the source virtual disk and snapshot repository virtual disk.) If you are monitoring total I/O per
and the RAID controller module owns snapshot virtual disks, the total I/O will include not only reads and writes to the snapshot virtual disk, but also RAID controller module read and write activity to the associated source virtual disk and snapshot repository virtual disk. - Virtual Disk thrashing---the condition where virtual disk ownership moves from one RAID controller module to a second RAID controller module, then back to the first RAID controller module---occurs if a source virtual disk and its associated snapshot virtual disk are mapped to different hosts, with a different preferred path assigned on each host. This situation occurs in a NetWare, HP-UX, or Linux environment when
is enabled, or in a Linux server cluster environment. Thrashing can lead to degraded system performance. To avoid virtual disk thrashing, the source virtual disk and snapshot virtual disk must have the same preferred path when mapped to one or more hosts.
The default snapshot repository virtual disk capacity is set to 20 percent of the source virtual disk, that is if enough free capacity exists to create a snapshot repository virtual disk of this size. The default threshold level for the snapshot repository virtual disk is set to 50 percent. If you are not sure how large to make the snapshot repository virtual disk or how high to set the snapshot repository virtual disk full warning, accept the default settings. You can estimate later how quickly the snapshot's repository capacity is being used. For more information, see Learn About Estimating Snapshot Repository Virtual Disk Life Expectancy.
Viewing Snapshot Virtual Disk Failure Settings
Important:
- Deleting a snapshot virtual disk automatically deletes the associated snapshot repository virtual disk.
- Deleting a snapshot repository virtual disk automatically deletes the associated snapshot virtual disk.
- Deleting a snapshot virtual disk and then creating it again forces you to stop the host application and unmount the source virtual disk while the snapshot is being created again.
- Re-creating a snapshot virtual disk alleviates the need to create a snapshot repository virtual disk, as well as re-map the assigned
between the snapshot virtual disk and the host. - After the snapshot virtual disk is re-created, you can change parameters on the snapshot repository virtual disk through the appropriate menu options.
- To avoid another "snapshot repository virtual disk capacity full" failure, increase the capacity of the snapshot repository virtual disk. For more information, see Increasing the Capacity of a Snapshot Repository Virtual Disk.
Use the following procedure to view the current failure settings.
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Select a snapshot repository virtual disk in the Logical View of the |
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Select Virtual Disk >> Properties. |
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Select Capacity tab to view the currently defined settings. |
If the snapshot repository virtual disk is set to fail the snapshot virtual disk when it becomes full, its data is not recoverable, and the snapshot cannot be accessed. The only available option (if this situation occurs) is to delete the snapshot virtual disk or re-create the snapshot virtual disk to create a new point-in-time image.
If the snapshot repository virtual disk is set to fail writes to the source virtual disk, the data is recoverable, but the snapshot repository virtual disk capacity must be increased before writes to the source virtual disk are not rejected. For more information, see Increasing the Capacity of a Snapshot Repository Virtual Disk.
Introduction to Snapshot Virtual Disks
Learn About Disabling and Re-creating a Snapshot Virtual Disk
Learn About Estimating Snapshot Repository Virtual Disk Life Expectancy
Increasing the Capacity of a Snapshot Repository Virtual Disk