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Veritas Access Administrator's Guide

Last Published: 2022-12-14

Product(s): Access (7.4.2.400)

Platform: Linux

About instant rollbacks

Instant rollbacks are volume-level snapshots. All rollback commands take a file system name as an argument and perform operations on the underlying volume of that file system.

Note:

If you plan to add a tier to the file system, add the tier first and then create the rollback. If you add the tier after a rollback exists, the rollback hierarchy would have inconsistencies because the rollback is not aware of the tier.

Both space-optimized and full-sized rollbacks are supported by Veritas Access. Space-optimized rollbacks use a storage cache, and do not need a complete copy of the original volume's storage space. However, space-optimized rollbacks are not suitable for write-intensive volumes, because the copy-on-write mechanism may degrade the performance of the volume. Full-sized rollbacks use more storage, but that has little impact on write performance after synchronization is completed.

Both space-optimized rollbacks and full-sized rollbacks can be used instantly after operations such as create, restore, or refresh.

Note:

When instant rollbacks exist for a volume, you cannot disable the FastResync option for a file system.

When creating instant rollbacks for volumes bigger than 1T, there may be error messages such as the following:

ACCESS instant_snapshot ERROR V-288-1487 Volume prepare for full-fs1-1 failed.

An error message may occur because the default amount of memory allocated for a Data Change Object (DCO) may not be large enough for such big volumes. You can use the vxtune command to change the value. The default value is 6M, which is the memory required for a 1T volume.

To change it to 15M, use the following command:

vxtune volpagemod_max_memsz `expr 15 \* 1024 \* 1024`