Silicon Graphics InfiniteStorage 4000 Series, Configuring And Maintaining

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Chapter 6: Using the Snapshot Images Premium Feature 113
 deleteCount
– This parameter deletes the oldest snapshot image first and
continues to delete the oldest snapshot images until reaching the number that you
enter. If the number that you enter is greater than the number of snapshot images,
all of the snapshot images are deleted.
 retainCount
– This parameter keeps the most recent snapshot images in the
consistency group.
If you have a snapshot volume associated with the associated consistency group you
can choose to keep or delete the snapshot volume. To keep the snapshot volume set
the
ignoreSnapVolume
parameter to
TRUE
. To delete the snapshot volume set the
ignoreSnapVolume
parameter to
FALSE
. The default is
FALSE
. This parameter
applies only if the consistency group snapshot image is associated with a consistency
group snapshot volume.
Creating a
Snapshot
Volume You create a snapshot volume to provide host access to a snapshot image within a
snapshot group. A
read-write
snapshot volume has its own repository that is used
to save any subsequent modifications made by the host application to the base volume
without affecting the referenced snapshot image.
You create a snapshot volume to provide host access to a snapshot image within a
snapshot group. A
read-write
snapshot volume has its own repository that is used
to save any subsequent modifications made by the host application to the base volume
without affecting the referenced snapshot image.
The snapshot volume can be designated as either
read-only
or
read-write
.

A
read-only
snapshot volume provides a host application with
READ
access
to a copy of the data contained in the snapshot image, but without the ability to
modify the snapshot image. A
read-only
snapshot volume does not have an
associated repository.

A
read-write
snapshot volume requires an associated repository to provide
the host application with
WRITE
access to a copy of the data contained in the
snapshot image.
Prerequisites

The Snapshot premium feature must be enabled on the local storage arrays.
Guidelines
Keep these guidelines in mind when creating a snapshot volume:

You cannot create a snapshot volume of a Failed base volume.

You can change the size of the snapshot repository. If you have the storage
capacity you can increase the size of the snapshot repository to avoid a repository
full message. Conversely, if you find that the snapshot volume repository is larger
than you need, you can reduce its size to free up space that is needed by other
logical volumes.