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alinmesser
n00b
Joined: 26 Jun 2004
Posts: 25
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 Posted: Wed Oct 24, 2007 12:12 am Post subject: Software RAID disk replacement missing superblock |
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Hi, I've using the linux (md) raid for many years now without any issues, but I just ran into one I cannot solve.
I have a 4 disk raid0 array, and one of the disks started developing bad sectors.
| Code: | Oct 23 03:23:26 homer hde: dma_intr: status=0x51 { DriveReady SeekComplete Error }
Oct 23 03:23:26 homer hde: dma_intr: error=0x40 { UncorrectableError }, LBAsect=294715424, high=17, low=9502752, sector=294715424 |
I was lucky enough to find an identical drive (Maxtor 6Y160P0) and I'm trying to replace the bad one.
I did:
| Code: | | dd if=/dev/hde of=/dev/hdc conv=noerror bs=512 |
only to find out that, for some unknown reasons, the extra-super-secret raid superblock is not being replicated with dd...
I found somewhere in the documentation that it is supposed to be located in the last 128k of the disk... but it's not, unless dd is not really as low-level as I thought.
Superblock output:
| Code: | mdadm -E /dev/hde
/dev/hdc:
Magic : a92b4efc
Version : 00.90.00
UUID : 12d85fe9:ded8f770:930cf5aa:44457eac
Creation Time : Mon Oct 2 16:10:26 2006
Raid Level : raid0
Used Dev Size : 0
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Update Time : Tue Jul 31 02:26:49 2007
State : active
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Checksum : fdff9f94 - correct
Events : 0.3
Chunk Size : 64K
Number Major Minor RaidDevice State
this 0 33 0 0 active sync /dev/hde
0 0 33 0 0 active sync /dev/hde
1 1 34 0 1 active sync /dev/hdg
2 2 56 0 2 active sync /dev/hdi
3 3 57 0 3 active sync /dev/hdk
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and, of course:
| Code: | mdadm -E /dev/hdc
mdadm: No md superblock detected on /dev/hdc
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Since it's a RAID0 I cannot add the disk and than mark the other one as failed.
I am afraid to do anything more drastic like zero-ing out the superblocks and re-creating the array, it must be a way to copy the disk.
Did any of you run into this before?
Thanks in advance
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MesseR |
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alinmesser
n00b
Joined: 26 Jun 2004
Posts: 25
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| Posted: Wed Oct 24, 2007 2:51 pm Post subject: Fixed |
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The problem was me not using the "sync" option for dd.
The correct way was:
| Code: | | dd if=/dev/hde of=/dev/hdc conv=noerror,sync bs=512 |
Whithout "sync", dd skips over the bad sectors in the input but doesn't seek ahead by a secotr in the output, so everything is skewed from that point on.
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MesseR |
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