On 8 Jul 2005, Melinda Taylor wrote:
> We have a computer based at the South Pole which has a degraded raid 5
> array across 4 disks. One of the 4 HDD's mechanically failed but we have
> bought the majority of the system back online except for the raid5
> array. I am pretty sure that data on the remaining 3 partitions that
> made up the raid5 array is intact - just confused. The reason I know
> this is that just before we took the system down, the raid5 array
> (mounted as /home) was still readable and writable even though
> /proc/mdstat said:
[...]
> /*[root@planet mdadm-1.12.0]# mdadm --assemble --force /dev/md2
> /dev/hdd5 /dev/hda5 /dev/hdb5 /dev/hdc5
> mdadm: no RAID superblock on /dev/hdc5
> mdadm: /dev/hdc5 has no superblock - assembly aborted
>
> *//dev/hdc is the new disk I have just installed to replace the failed
> one (/dev/hda). I have parititioned it correctly and in fact one
> partition on /dev/hdc1 is now happily part of another raid1 set on the
> system so I know all is good with /dev/hdc
What you want to do is start the array as degraded, using *only* the
devices that were part of the disk set. Substitute 'missing' for the
last device if needed but, IIRC, you should be able to say just:
] mdadm --assemble --force /dev/md2 /dev/hd[abd]5
Don't forget to fsck the filesystem thoroughly at this point. :)
Once the array is up and running, you *then* add the new disk to it by
saying:
] mdadm -a /dev/md2 /dev/hdc5
The array will then recover and, hopefully, life is good.
Daniel
--
Anyone who goes to a psychiatrist ought to have his head examined.
-- Samuel Goldwyn
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