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Recovery time

Several "best practice" rules enable you to check that your storage configuration has the resilience to withstand a disk failure or a system failure.

Checking for multiple RAID-5 logs on a physical disk (vxse_disklog)

To check whether more than one RAID-5 log exists on the same physical disk, run rule vxse_disklog.

RAID-5 log mirrors for the same physical volume should be located on separate physical disks to ensure redundancy. More than one RAID-5 log on a disk also makes the recovery process longer and more complicated.

Checking for large mirror volumes without a dirty region log (vxse_drl1)

To check whether large mirror volumes (larger than 1GB) have an associated dirty region log (DRL), run rule vxse_drl1.

Creating a DRL speeds recovery of mirrored volumes after a system crash. A DRL tracks those regions that have changed and uses the tracking information to recover only those portions of the volume that need to be recovered. Without a DRL, recovery is accomplished by copying the full contents of the volume between its mirrors. This process is lengthy and I/O intensive.

See "Preparing a volume for DRL and instant snapshots" on page 285.

Checking for large mirrored volumes without a mirrored dirty region log (vxse_drl2)

To check whether a large mirrored volume has a mirrored DRL log, run rule vxse_drl2.

Mirroring the DRL log provides added protection in the event of a disk failure.

See "Preparing a volume for DRL and instant snapshots" on page 285.

Checking for RAID-5 volumes without a RAID-5 log (vxse_raid5log1)

To check whether a RAID-5 volume has an associated RAID-5 log, run rule vxse_raid5log1.

In the event of both a system failure and a failure of a disk in a RAID-5 volume, data that is not involved in an active write could be lost or corrupted if there is no RAID-5 log.

See "Adding a RAID-5 log" on page 293.

Checking minimum and maximum RAID-5 log sizes (vxse_raid5log2)

To check that the size of RAID-5 logs falls within the minimum and maximum recommended sizes, run rule vxse_raid5log2.

The recommended minimum and maximum sizes are 64MB and 1GB respectively. If vxse_raid5log2 reports that the size of the log is outside these boundaries, adjust the size by replacing the log.

Checking for non-mirrored RAID-5 logs (vxse_raid5log3)

To check that the RAID-5 log of a large volume is mirrored, run the vxse_raid5log3 rule.

A mirror of the RAID-5 log protects against loss of data due to the failure of a single disk. You are strongly advised to mirror the log if vxse_raid5log3 reports that the log of a large RAID-5 volume does not have a mirror.

See "Adding a RAID-5 log" on page 293.