RAID 1, how to verify mirror , silent corruption

homerwsmith · 10-23-2011, 02:09 PM

Dear Gentle Folk,

Running CentOS 5.x with mdadm for raid 1.

Is there any way to verify a raid 1 array of
two disks to verify that they are exact copies?

Need to do this on the fly while the array is
running and in service.

Being paranoid, in the past bad data has gotten
on one disk and not the other due to bad motherboard
or whatever.

Pointers to RTFM welcome,

Thanks in advance to all who read this.

Homer W Smith
Lightlink Internet

macemoneta · 10-24-2011, 07:11 AM

Yes, you can check and correct the array with:

Code:

echo check > /sys/block/md0/md/sync_action

Wait for the check to complete:

Code:

cat /sys/block/md0/md/sync_action
idle

Check for any block mismatches:

Code:

cat /sys/block/md0/md/mismatch_cnt
0

If you get a non-zero value, run:

Code:

echo repair > /sys/block/md0/md/sync_action

The above can be performed while the array is in use.

homerwsmith · 12-01-2011, 10:41 PM

Thanks for the below.

As far as I know CentOS5.x does not have /sys or /proc/sys or any /proc/*/block/*

Any other suggestions?

Thanks in advance.

Homer

Quote:

Originally Posted by macemoneta

Yes, you can check and correct the array with:

Code:

echo check > /sys/block/md0/md/sync_action

Wait for the check to complete:

Code:

cat /sys/block/md0/md/sync_action
idle

Check for any block mismatches:

Code:

cat /sys/block/md0/md/mismatch_cnt
0

If you get a non-zero value, run:

Code:

echo repair > /sys/block/md0/md/sync_action

The above can be performed while the array is in use.

macemoneta · 12-01-2011, 11:59 PM

Quote:

Originally Posted by homerwsmith

Thanks for the below.

As far as I know CentOS5.x does not have /sys or /proc/sys or any /proc/*/block/*

Any other suggestions?

Thanks in advance.

Homer

CentOS 5 does have /sys. Have you mounted it in /etc/fstab?