Help With Degraded Linux Raid

[Netopia]

Hi guys,

I posted this over on the OS forum, but since I've not gotten any bites and this is a fairly technical situation, I thought I'd throw it to the uberTechies and see if there are any ideas.

I'm not quite sure what to do. I've got a system with two drives setup in Raid-1. I had some hiccups on the machine the other day and now I've got this situation (weird, no "attach code" button on the the HT forum!).

[root@mailscan spamassassin]# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.03
Creation Time : Wed Feb 1 09:12:45 2006
Raid Level : raid1
Array Size : 521984 (509.75 MiB 534.51 MB)
Device Size : 521984 (509.75 MiB 534.51 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Wed Feb 22 11:46:34 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

UUID : e160107f:ba11b455:737aa518:cf303a9e
Events : 0.1245

Number Major Minor RaidDevice State
0 3 1 0 active sync /dev/hda1
1 22 1 1 active sync /dev/hdc1


======================================

[root@mailscan spamassassin]# mdadm --detail /dev/md1
/dev/md1:
Version : 00.90.03
Creation Time : Wed Feb 1 09:11:00 2006
Raid Level : raid1
Array Size : 75778496 (72.27 GiB 77.60 GB)
Device Size : 75778496 (72.27 GiB 77.60 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 1
Persistence : Superblock is persistent

Update Time : Thu Feb 23 11:36:35 2006
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 1
Spare Devices : 0

UUID : cf8eee85:e40bd94b:58db741c:9f412b4b
Events : 0.790890

Number Major Minor RaidDevice State
0 0 0 - removed
1 22 3 1 active sync /dev/hdc3

2 3 3 - faulty /dev/hda3

So how do I remirror just one device out of a whole disk? Any ideas? The thing that really stinks is that it is on the boot drive!

Thanks in advance for any thoughts.

Joe

 

[nd]

This is confusing. /dev/hda1 seems to be fine, but it lists /dev/hda3 as "faulty". So the disk itself isn't bad -- maybe just the filesystem on the hda3 mirror is corrupted?

Shouldn't it be harmless to rebuild the array on the whole /dev/hda since you're using RAID-1? i.e erasing the superblock and essentially starting over.

 

[Netopia]

It may be... except that hda1 is where the system boots from, so I'll have to temporarily redo the system to boot from the other drive. I was just hoping there was a way I could simply resync hdc3 --> hda3 so that I wouldn't have to completely remirror the entire drive.

As it is, if I have to redo the whole drive, I think I'll replace both drives with new ones... these two are a couple years old and if I'm going to go through the trouble of resyncing, I might as well remove the possibility that these drives might fail.

Joe

 

[nd]

The fact that it's the boot drive shouldn't matter much. Do you have any Knoppix CDs handy? They're perfect for this sort of situation. I would just burn a Knoppix CD, boot it and recover from there.

 

[Netopia]

I've got quite a few live linux CD's on hand, including Knoppix. Getting in isn't the problem though... it's whether or not I can repair and resync ONLY /dev/hda3 and not have to redo the whole drive.

Joe

 

[nd]

I think you should be able to fix this with:

# Clear out corrupt hda3
$ dd if=/dev/zero of=/dev/hda3

# Rebuild array
$ mdadm --manage /dev/md1 --add /dev/hda3

Then cat /proc/mdstat and watch the progress.