Re: Paranoia about DegradedArray
On Wed, 29 Oct 2008 13:00:25 -0400, Hal Vaughan wrote:
> On Wednesday 29 October 2008, Hendrik Boom wrote:
>> I got the message (via email)
>>
>> This is an automatically generated mail message from mdadm running on
>> april
>>
>> A DegradedArray event had been detected on md device /dev/md0.
>>
>> Faithfully yours, etc.
>>
>> P.S. The /proc/mdstat file currently contains the following:
>>
>> Personalities : [raid1]
>> md0 : active raid1 hda3[0]
>> 242219968 blocks [2/1] [U_]
>>
>> unused devices: <none>
>>
>>
> You don't mention that you've checked the array with mdadm --detail
> /dev/md0. Try that and it will give you some good information.
april:/farhome/hendrik# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.03
Creation Time : Sun Feb 19 10:53:01 2006
Raid Level : raid1
Array Size : 242219968 (231.00 GiB 248.03 GB)
Device Size : 242219968 (231.00 GiB 248.03 GB)
Raid Devices : 2
Total Devices : 1
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed Oct 29 13:23:15 2008
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
UUID : 4dc189ba:e7a12d38:e6262cdf:db1beda2
Events : 0.5130704
Number Major Minor RaidDevice State
0 3 3 0 active sync /dev/hda3
1 0 0 1 removed
april:/farhome/hendrik#
So from this do I conclude that /dev/hda3 is still working, but that it's
the other drive (which isn't identified) that has trouble?
I'm a bit surprised that none of the messages identifies the other
drive, /dev/hdc3. Is this normal? Is that information available
somewhere besides the sysadmin's memory?
>
> I've never used /proc/mdstat because the --detail option gives me more
> data in one shot. From what I remember, this is a raid1, right? It
> looks like it has 2 devices and one is still working, but I might be
> wrong. Again --detail will spell out a lot of this explicitly.
>
>> Now I gather from what I've googled that somehow I've got to get the
>> RAID to reestablish the failed drive by copying from the nonfailed
>> drive. I do believe the hardware is basically OK, and that what I've
>> got is probably a problem due to a power failure (We've had a lot of
>> these recently) or something transient.
>>
>> (a) How do I do this?
>
> If a drive has actually failed, then mdadm --remove /dev/md0 /dev/hdxx.
> If the drive has not failed, then you need to fail it first with --fail
> as an option/switch for mdadm.
So presumably the thing to do is
mdadm --fail /dev/md0 /dev/hdc3
mdadm --remove /dev/md0 /dev/hdc3
and then
mdadm --add/dev/md0 /dev/hdc3
Is the --fail really needed in my case? the --detail option seems to
have given /dev/hdc3 the status of "removed" (although it failed to
mention is was /dev/hdc3).
>
>> (b) is hda3 the failed drive, or is it the one that's still working?
>
> That's one of the things mdadm --detail /dev/md0 will tell you. It will
> list the active drives and the failed drives.
Well. I'm glad I was paranoid enough to ask. It seems to be the drive
that's working. Glas I didn't try to remove and add in *that* one.
Thanks,
-- hendrik
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