VERITAS Volume Manager 3.5 Installation Guide (September 2004)

Getting Started with VxVM

Protecting Your System and Data

Chapter 5

Protecting Your System and Data

VxVM can protect your system from loss of data due to disk failure.

The following are suggestions for protecting your data:

• Use mirroring to protect data against loss from a disk failure. To preserve data, create and use

mirrored volumes that have at least two data plexes. The plexes must be on different disks. If a

disk failure causes a plex to fail, the data in the mirrored volume still exists on the other disk.

When you use the vxassist mirror command to create mirrors, it locates the mirrors so the loss

of one disk does not result in a loss of data. By default, the vxassist command does not create

mirrored volumes; edit the file /etc/default/vxassist to set the default layout to mirrored.

For information on the vxassist defaults file, see the VERITAS Volume Manager Administrator’s

Guide and the vxassist(1M) manual page.

• Leave the VxVM hot-relocation feature enabled to detect disk failures automatically. It will notify

you of the nature of the failure, attempt to relocate any affected subdisks that are redundant, and

initiate recovery procedures. Configure at least one hot-relocation spare disk in each disk group.

This will allow sufficient space for relocation in the event of a failure.

If the root disk is mirrored, hot-relocation can automatically create another mirror of the root disk

if the original root disk fails. The rootdg must contain enough contiguous spare or free space for

the volumes on the root disk (rootvol and swapvol volumes require contiguous disk space).

• Use the Dirty Region Logging (DRL) feature to speed up recovery of mirrored volumes after a

system crash. Make sure that each mirrored volume has at least one log subdisk.

NOTE usr volumes cannot be DRL volumes.

• Use logging to prevent corruption of recovery data in RAID-5 volumes. Make sure that each

RAID-5 volume has at least one log plex.

Perform regular backups to protect your data. Backups are necessary if all copies of a volume are

lost or corrupted. Power surges can damage several (or all) disks on your system. Also, typing a

command in error can remove critical files or damage a file system directly. Performing regular

backups ensures that lost or corrupted data is available to be retrieved.