Symantec Backup Exec

Have Backup Exec calculate the initial and maximum size of the cache file

Enables Backup Exec to automatically calculate the initial and maximum size of the cache file for each backup.

If the cache file is located on the volume that is being snapped, Backup Exec uses the following calculation:

For both the initial and maximum size, Backup Exec calculates 30 percent of the used space and 90 percent of the free space, and then uses the smaller number.

If the cache file is located on a different volume than the volume that is being snapped, Backup Exec uses the following calculations:

The initial size is zero. For the maximum size, Backup Exec calculates 30 percent of the free space on the target volume and uses that figure.

The maximum size cannot be smaller than the initial size. If the maximum size is calculated to be smaller than the initial size, Backup Exec sets the maximum size to match the initial size. Both the initial size and the maximum size must be at least 50 MB.

See About the Symantec Volume Snapshot Provider cache file location .

Initial size of the cache file (1 – 100 percent):

Sets the initial size of the cache file.

If you choose not to use the default, then type the percentage of free space that you want the Advanced Open File Option (AOFO) to use to create the cache file.

Increase this percentage if you receive an error message stating that AOFO is out of disk space. This increase enables additional free space to be allocated on the volume, which can then be used during the backup.

Symantec recommends that you set the maximum size before setting the initial size.

Maximum size that the cache file can grow to:

Sets the maximum size of the cache file.

If you do not use the default, then type the maximum percentage to allow for the cache file. If the snapshot exceeds the maximum percentage, the job will fail and the error will be listed in the job log.

If the cache file is located on the volume that is being snapped, Backup Exec uses the number that you type in this field to calculate the percentage of used space on the volume. Backup Exec also calculates 90 percent of the free space on the volume and uses the smaller number.

If the cache file is located on a different volume than the volume that is being snapped, Backup Exec uses the number that you type in this field to calculate the percentage of free space on the volume and uses that number.

The maximum size cannot be smaller than the initial size. If the maximum size is calculated to be smaller than the initial size, Backup Exec sets the maximum size to match the initial size. The maximum size must be at least 50 MB.

Number of seconds during which there can be no disk activity before the snapshot is created

Sets the minimum length of quiet time in seconds, in which the application waits for disk inactivity before the snapshot is created.

During this time, AOFO is waiting for there to be no drive activity to ensure that all buffers have been flushed, and therefore all the data on the drive should be consistent. The default quiet time is five seconds. In some cases it is necessary to lower this setting, but this increases the risk of the data on the drive becoming inconsistent. Decrease this setting if you have an active disk so that the snapshot can be created before reaching the maximum length of quiet time.

The recommended minimum length is five seconds, but you can choose between two and four seconds. This setting should never be lowered below two. Instead, investigate what applications or services may be causing excessive disk writes.

You may also want to select the option Process logical volumes for backup one at a time. This option enables the backup of multiple volumes in one job, while creating a snapshot of only one logical volume at a time and increases the ability to meet the minimum quiet time needed to complete a snapshot.

See Setting default options for the Advanced Open File Option.

Number of seconds that the application tries to obtain the minimum quiet time, after which the job fails

Sets the maximum length of time that AOFO waits for disk inactivity before terminating the creation of the snapshot. Increase this setting if a backup fails repeatedly with the message that it could not obtain the minimum quiet time. Increasing this setting maximizes the length of time used to create the snapshot. The default is 2,000 seconds.