I would re-create md0 array with a missing disk as follows:

mdadm -C /dev/md0 -l 1 -n 2 /dev/hdc2 missing

Later you can hot add a disk to make it a normal 2-way mirror array.

--
Regards,
Mike T.

On Mon, 2004-10-18 at 17:56, Konstantin Olchanski wrote:

Dear Linux raiders- I ran into a problem with raid1 recovery after
a disk failure (running Fedora2, kernel 2.6.8-1.521smp).

1) I had a raid1 filesystem mirrored across /dev/hda2 and /dev/hdc2.
2) Disk hda died (unreadable sectors, fails SMART tests)
3) A new blank hda was installed and partitionned exactly like hdc.
4) I cannot restart and rebuild the raid1 volume because hdc2 is
   in a funny "spare" state (see below)

How do I mark hdc2 as "active"?
Once "active", I assume then I will be able to restart md0,
hot-add /dev/hda2 as usual. (And the mirror will resync and rebuild itself?
Hopefully?)

[root@tw04 root]# mdadm -E /dev/hdc2
/dev/hdc2:
          Magic : a92b4efc
        Version : 00.90.00
           UUID : aade8782:20122089:4f496788:228d85b9
  Creation Time : Fri Oct  8 17:12:56 2004
     Raid Level : raid1
    Device Size : 124158208 (118.41 GiB 127.14 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0

    Update Time : Mon Oct 18 06:04:35 2004
          State : clean, no-errors
 Active Devices : 1
Working Devices : 2
 Failed Devices : 1
  Spare Devices : 1
       Checksum : 7041db42 - correct
         Events : 0.312429


      Number   Major   Minor   RaidDevice State
this     2      22        2        2      spare   /dev/hdc2
   0     0       3        2        0      active sync   /dev/hda2
   1     1       0        0        1      faulty removed
   2     2      22        2        2      spare   /dev/hdc2
[root@tw04 root]#