The instant snapshot feature enables you to take instant full snapshots, instant space-optimized snapshots, or instant plex-breakoff snapshots. The advantages of this method compared to the traditional method are:
The instant snapshot feature provided by VVR can be used either from the Primary or the Secondary. VVR also provides you with the option to take space-optimized snapshots.
The types of instant snapshots that you can create are:
If an RVG consists of only VxVM ISP volumes, you can perform only the instant full snapshot operation and the instant space-optimized snapshot operations. When creating the instant space-optimized snapshot, you must create the VxVM ISP cache object before proceeding with the operation as VVR does not support the
cachesize parameter for an RVG with VxVM ISP volumes.
The instant full snapshot feature of VVR enables you to create a full snapshot of all the data volumes in an RVG without any delay. In this case, the snapshot plexes do not require synchronization before creating the snapshot. Therefore, the required data is available instantly after the snapshot is created. However, this method requires the snapshot volumes to be created with the appropriate naming convention, before you proceed with the snapshots. For more information on creating instant full snapshots, refer to the section Instant full snapshot.
VVR also enables you to take instant space-optimized snapshots. Unlike instant full snapshots, the instant space-optimized snapshots require less storage space than the original volume because space-optimized snapshots store only the data that has changed between the original volume and the snapshot. Typically, the data that has changed between the original volume and the snapshot volume over the lifetime of the snapshot is minimal compared to the total data on the volume. Thus, the space-optimization achieved can be significant. The snapshot data is managed by VVR using a cache object which functions as a space-optimized persistent store. You must create the cache object before you take the instant space-optimized snapshots or specify the size of the cache object. Multiple snapshots can be created on the same cache object. The cache object can be created with an
autogrow option set to
on to allow it to grow automatically if the cache volume size is not enough for the specified writes. For more information on the cache object, refer to the section Preparing the RVG volumes for snapshot operation. For more information on creating instant space-optimized snapshots, refer to the section Creating instant space-optimized snapshots.
Similar to the traditional plex-breakoff snapshot feature, this method also requires the plexes to be attached to the source volume before taking the snapshots. Although the synchronization of the plexes may still take a long time, the major difference between the traditional snapshots and the instant plex-breakoff snapshots is that you can instantly start performing the operations such as refresh, restore, and snapback on the instant plex-breakoff snapshots.
The instant plex-breakoff snapshots operation requires the plexes to be named using the
plexprefix attribute if you want to use specific plexes. Otherwise, VVR uses the plexes that are in the snapdone state. For more information on creating the instant plex-breakoff snapshots, refer to the section Instant plex-breakoff snapshots.