John Hughes [off-list ref] wrote:

This works, but when I look at the results it looks rather ugly, the new 
disk goes in a new "slot" in the raid superblock.  Is it the case that 

This is not a dumb question. This is just unexpected behaviour :)
I have the same here on a 1.1 superblock RAID1

Before:
md0 : active raid10 sdw[11] sdg[10] sdv[9] sdf[8] sdu[7] sde[6] sdt[5] sdd[4] sds[3] sdc[2] sdr[1] sdb[0]
      426970368 blocks super 1.2 64K chunks 2 near-copies [12/12] [UUUUUUUUUUUU]
      bitmap: 1/204 pages [4KB], 1024KB chunk
After:
md0 : active raid10 sdh[12] sdw[11] sdg[10] sdv[9] sdf[8] sdu[7] sde[6] sdt[5] sdd[4] sds[3] sdr[1] sdb[0]
      426970368 blocks super 1.2 64K chunks 2 near-copies [12/12] [UUUUUUUUUUUU]
      bitmap: 0/204 pages [0KB], 1024KB chunk

In my case I created the array as:

# uname -a
Linux darkside 2.6.30-1-686 #1 SMP Sat Aug 15 19:11:58 UTC 2009 i686 GNU/Linux
# mdadm --create -e 1.1 -l raid1 -n 2 -b internal -a md /dev/md9 /dev/hdh missing

and subsequently added /dev/sdd.

/proc/mdstat:
md9 : active raid1 sdd[2] hdh[0]
      312571092 blocks super 1.1 [2/2] [UU]
      bitmap: 1/299 pages [4KB], 512KB chunk

# mdadm -E /dev/hdh /dev/sdd
/dev/hdh: 
          Magic : a92b4efc
        Version : 1.1
    Feature Map : 0x1
...
     Raid Level : raid1
   Raid Devices : 2
...
    Data Offset : 264 sectors
   Super Offset : 0 sectors
          State : clean
...
Internal Bitmap : 8 sectors from superblock
    Update Time : Fri Sep 18 20:14:24 2009
       Checksum : 754e56a3 - correct
         Events : 12564
...
   Device Role : Active device 0
   Array State : AA ('A' == active, '.' == missing)
/dev/sdd: 
          Magic : a92b4efc
        Version : 1.1
    Feature Map : 0x1
...
     Raid Level : raid1
   Raid Devices : 2
...
    Data Offset : 264 sectors
   Super Offset : 0 sectors
          State : clean
...
Internal Bitmap : 8 sectors from superblock
    Update Time : Fri Sep 18 20:14:24 2009
       Checksum : 8747d7b3 - correct
         Events : 12564
...
   Device Role : spare
   Array State : AA ('A' == active, '.' == missing)

`mdadm -A --update=summaries' doesn't help (I didn't expect it to, tho)
`mdadm -A --update=resync' doesn't help
`--fail --remove --add' doesn't help
`--fail --remove --grow -n 1 --grow -n 2 --add' doesn't help
`--fail --remove --grow -n 1 --add --grow -n 2' doesn't help

The array resyncs the few bitmap-chunks and the component remains in
slot 2, the array has no device missing, the bitmap stays at 1 page
(1620 bits set). Writing to the array increases the bits set for a short
time and then they go back to 1 page (1620 bits) and remain there.
The components are in sync and remain in sync, I cmp'ed them.


regards
   Mario
-- 
Damit das Mögliche entsteht, muß immer wieder das Unmögliche versucht werden.
                                                  -- Hermann Hesse

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