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Old 10-23-2011, 02:09 PM   #1
homerwsmith
LQ Newbie
 
Registered: Aug 2010
Posts: 14

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RAID 1, how to verify mirror , silent corruption


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
 
Old 10-24-2011, 07:11 AM   #2
macemoneta
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Registered: Jan 2005
Location: Manalapan, NJ
Distribution: Fedora x86 and x86_64, Debian PPC and ARM, Android
Posts: 4,593
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Rep: Reputation: 332Reputation: 332Reputation: 332Reputation: 332
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.
 
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Old 12-01-2011, 10:41 PM   #3
homerwsmith
LQ Newbie
 
Registered: Aug 2010
Posts: 14

Original Poster
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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 View Post
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.
 
Old 12-01-2011, 11:59 PM   #4
macemoneta
Senior Member
 
Registered: Jan 2005
Location: Manalapan, NJ
Distribution: Fedora x86 and x86_64, Debian PPC and ARM, Android
Posts: 4,593
Blog Entries: 2

Rep: Reputation: 332Reputation: 332Reputation: 332Reputation: 332
Quote:
Originally Posted by homerwsmith View Post
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?
 
  


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