Dell PowerVault MD Series, Administrator'S Manual

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subsequent modifications made by the host application to the base virtual disk without affecting the referenced
snapshot image. Each member repository is created when the consistency group snapshot virtual disk is created.
Ranking Repository Candidates
If you choose to create a repository manually, you can filter repository candidates for each member virtual disk by
selecting either a percentage of the base virtual disk capacity or by specifying a preferred capacity in the Snapshot
Group Settings window. Based on your selection, best repository candidates are displayed. Repository candidates
shown contain both new and existing repository virtual disks residing on a disk group or disk pool.
For more information, see the online help topics.
Using Snapshot Consistency Groups With Remote Replication
Although a virtual disk can belong to multiple consistency groups, you must create separate consistency groups for
snapshot images and Remote Replication.
Adding a base virtual disk containing a consistency group to a Remote Replication (non-legacy, asynchronous), the
repository automatically purges the oldest snapshot image and sets the auto-delete limit to the maximum allowable
snapshot limit for a consistency group.
Additionally, all member virtual disks belonging to both a snapshot consistency group and a Remote Replication group
must belong to the same Remote Replication group.
Creating Snapshot Images
A snapshot image is a logical point-in-time image of the content of an associated base virtual disk. With snapshot
images, you can create multiple copies of production data on your storage array much more quickly than full copies.
Snapshot images track source changes from the time each snapshot image is created. You can create snapshot images
for the following storage objects:
• Standard virtual disks
• Thin virtual disks
• Consistency groups
Before creating a snapshot image, consider these guidelines:
• If you attempt to create a snapshot image on a snapshot group and that snapshot group has reached its
maximum number of snapshot images, you can retry creating snapshot images after doing one of the following:
– Enable automatic deletion of snapshot images in the Advanced Options section of the Create wizard.
– Manually delete one or more snapshot images from the snapshot group.
• If you attempt to create a snapshot image and either of the following conditions below are present, the creation
may remain in Pending state:
– The base virtual disk that contains this snapshot image is a member of an Remote Replication group.
– The base virtual disk is currently synchronizing. When synchronization is complete, the snapshot image
creation will complete.
• You cannot create a snapshot image on a failed virtual disk or on a snapshot group designated as Reserved.
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