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util-linux package

Degraded raid, which disk is at fault?

Asked by Peter Horsley

I'm using Ubuntu 10.04 LTS to run a RAID 5 (5 * 2Tb Hdds) array. Recently, I noticed in Disk Utility that the raid array state is listed as DEGRADED (in red). I assume this means one of the drives has failed, but clicking each drive to view status information doesn't tell me which one is at fault. How do I figure out what is wrong and get my raid back to normal state?

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Peter Horsley
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Revision history for this message
actionparsnip (andrew-woodhead666) said : 		#1

Do you use a hardware raid or is it fake or software raid?

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Peter Horsley (peter-g-horsley) said : 		#2

Just software raid. I noticed there's a 'check array' button in Disk Utility. Not sure if clicking that would tell me more information about the cause...

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actionparsnip (andrew-woodhead666) said : 		#3

You could use the drive manufacturers tool on the ultimate boot cd to test the drives mechaically, depends what is meant by 'degraded'. If you had a decent raid card you could as that and it would tell you.

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Peter Horsley (peter-g-horsley) said : 		#4

I found that you can use this command:

sudo mdadm -D /dev/md0

to show the status of each drive in the raid. In my case it shows:

    Number Major Minor RaidDevice State
       0 8 1 0 active sync /dev/sda1
       1 0 0 1 removed
       2 8 65 2 active sync /dev/sde1
       3 8 49 3 active sync /dev/sdd1
       5 8 33 4 active sync /dev/sdc1

       6 8 81 - faulty spare /dev/sdf1

So it's /dev/sdf1 that I will replace. Thank you.