Maximum Cache Size

The Maximum Cache Size is the maximum for the VSP cache file to grow to when creating snapshots. The Maximum Cache Size is an optional configuration property and is only applicable when the VSP cache file is placed on a volume that is not being snapped. When the VSP cache file is placed on a volume that is not being snapped, the cache file size begins at 0 megabytes and can grow to a maximum size of Maximum Cache Size.

This property appears for Windows clients only.

The Maximum Cache Size is calculated as a percentage of free disk space (of the cache file volume) from the value specified in Maximum Cache Size if the form of measurement used is percentage of disk space. The Maximum Cache Size is calculated in megabytes if the form of measurement selected is Cache Size in MB.

If the Customize Cache Size property is disabled, NetBackup automatically determines Maximum Cache Size for the VSP snapshot if the cache file is being placed in a volume that is not being snapped.

The following items are VSP best practices when configuring VSP cache sizes:

• Allow NetBackup to automatically determine cache file sizes for VSP snapshots by disabling the Customize Cache Size property. This allows NetBackup to allocate as much cache space as possible whenever creating VSP snapshots. In most cases, allowing NetBackup to automatically size cache files should avoid VSP snapshot errors from occurring. However, in some cases, VSP snapshot errors could occur (even if Customize Cache Size is disabled), depending on the data being backed up and the I/O activity of the client being backed up.
• If snapshot errors still occur even if Customize Cache Size is disabled, then increase the Initial Cache Size and Maximum Cache Size properties to values that best fit your client's installation. The recommended setting for the Initial Cache Size is 30% of used disk space of the volume that is being snapshot (the cache file size will the be value set at the Initial Cache Size if the VSP cache file is placed in the same volume as being snapshot. It will be ignored otherwise). The recommended setting for Maximum Cache Size is 95% of free disk space of the cache file volume (the cache file will begin at 0 MB and will grow until a maximum of Maximum Cache Size if the cache file is placed on a different volume that is being snapshot. It will be ignored otherwise).
• Use caution when manually configuring the cache file sizes since they are used regardless of the sizes of the volumes being backed up. If enough space is not allocated, the backup job could fail with a VSP error.