Strange ZFS behaviour when a drive fail.

[Ståle Kristoffersen]

Hi, I have a a zpool containing two raidz-set, and one of the drive died.
After a reboot the controller removed the disk and renumbered the other:
        NAME                     STATE     READ WRITE CKSUM
        media                    DEGRADED     0     0     0
          raidz1                 DEGRADED     0     0     0
            mfid1                ONLINE       0     0     0
            6496191869544847902  FAULTED      0     0     0  was /dev/mfid2
            mfid2                ONLINE       0     0     0
            mfid3                ONLINE       0     0     0
          raidz1                 ONLINE       0     0     0
            mfid4                ONLINE       0     0     0
            mfid5                ONLINE       0     0     0
            mfid6                ONLINE       0     0     0
            mfid7                ONLINE       0     0     0

I have since gotten the drive online (as mfid8) and now strangely zfs reports that it is resilvering:
 scrub: resilver in progress, 1,11% done, 307445734561825779h49m to go
But to what drive?
zpool iostat shows that it reads alot from all the drives in the first raidz:

                            capacity     operations    bandwidth
pool                      used  avail   read  write   read  write
-----------------------  -----  -----  -----  -----  -----  -----
media                    3,87T   949G    299     11  35,5M  51,4K
  raidz1                 3,39T   253G    283      9  35,4M  46,8K
    mfid1                    -      -    148     15  11,8M  33,9K
    6496191869544847902      -      -      0      0  2,49K      0
    mfid2                    -      -    147     15  11,8M  33,5K
    mfid3                    -      -    147     16  11,8M  32,3K
  raidz1                  495G   695G     16      1   111K  4,63K
    mfid4                    -      -     10      1   336K  2,70K
    mfid5                    -      -     10      1   344K  2,70K
    mfid6                    -      -     11      1   385K  2,64K
    mfid7                    -      -     11      1   390K  2,22K

This seems strange to me.

PS: I then ran zpool replace media 6496191869544847902 mfid8 and got back:
cannot replace 6496191869544847902 with mfid8: mfid8 is busy

when I then ran zpool status I got:
 scrub: resilver completed with 0 errors on Wed Mar 26 15:15:50 2008

Why did it start to resilver onto "nothing", and why can't I replace it with mfid8 (even with -f)?
-- 
Ståle Kristoffersen