• KVM Host Raid Consistency Checking

KVM Host Raid Consistency Checking

The Problem

Eventually a disk will fail, but in some cases a sector on a disk just goes bad without being used, and noone knows...

Consider the following.

* A sector on disk A goes bad. The sector is not used yet. * A sector on disk B goed bad. The sector on disk B is used. * Raid software will take disk B out of the array. * A new disk is added to replace disk B. * Resyncing from disk A to disk B is started. * Resyncing reaches bad sector on disk A, * Resyncing is now impossible.

The solution

Run regular raid consistency checks. I run this on tuesday night. Edit your crontab.

# crontab -e

Add the following to your crontab

0 4 * * 2 echo "check" > /sys/block/md0/md/sync_action
0 4 * * 2 echo "check" > /sys/block/md1/md/sync_action