Degraded Array Problem for mdadm


I have a software RAID1 installed over two disks. Everything appears to be functioning correctly, except that I got these emails:
From root@localhost.localdomain  Wed Nov 24 11:28:08 2004
Date: Wed, 24 Nov 2004 11:28:02 +1100
From: mdadm monitoring <root@localhost.localdomain>
To: root@localhost.localdomain
Subject: DegradedArray event on /dev/md4:hal

This is an automatically generated mail message from mdadm
running on hal

A DegradedArray event had been detected on md device /dev/md4.

Faithfully yours, etc.

Nothing appears to be broken in terms of use, but naturally I am concerned about degraded arrays coming up.

Can someone please help me identify either the problem, or if there is no problem clarrify things?

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That probably indicates that an error occured on the one the disks in the RAID. You can see which disk has the prblem by looking at what 'more /proc/mdstat' shows.

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I agree with jlevie. It probably isn't something to worry about too much to begin with, but it is a good Idea for you to monitor these type of messages, and if they start howing up more and more frequently it may be a good idea to look around for a new, spare drive.

Since you have raid1 your system should keep running even if one of your disks is broken, but once a disk is broken it is important to act immediately. If by inspecting the errors with jlevie's command you see those errors on both disks, and the errors increase, you should replace one of your drives while both original disks are still running.
madm saying that one of the volumes is operating in degraded mode means that there's been errors on one of the pairs. Sometimes that can be a transient failure and rebuilding the volume will work. Other times that is the result of bad blocks one one of the disks. And with IDE disks this is frequently a sign that the disk will completely fail in the near future. Therefore this is something that needs to be investigated and dealt with immediately.
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