On 08/14/2014 07:19 PM, NeilBrown wrote:
On Thu, 14 Aug 2014 18:08:30 -0500 Ram Ramesh <rramesh2400@xxxxxxxxx> wrote:
Hi,
I just finished converting a 3-disk raid5 to 4-disk raid6. After a
reboot to start clean, I noticed that one of the disk (the new one I
just added) was missing in /proc/partitions. This was disk 4 in my
/dev/md0. Assuming some cable issue, I powered off, wiggled the cables
and restarted and the device was found by kernel. However, md0 shows
device missing and array degraded
lata [rramesh] 280 > cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid6 sdb1[0] sdd1[3] sdc1[1]
3906763776 blocks super 1.2 level 6, 512k chunk, algorithm 2
[4/3] [UUU_]
unused devices: <none>
However my attempt to --re-add does not work.
lata [rramesh] 277 > sudo mdadm /dev/md0 --verbose --re-add /dev/sde1
mdadm: --re-add for /dev/sde1 to /dev/md0 is not possible
"re-add" only makes sense when you have a write-indent bitmap which you don't
have.
So you need to "--add" which marks the device as a spare and then starts a
complete rebuild.
I checked the SMART and it shows a lot of reallocated_sector_ct errors
also. So, the disk is dying, but I am not able understand why mdadm
would not add.
It will "add". It just wont "re-add".
NeilBrown
Thanks. Did not know that. I thought it will add without rebuild. This
means if a cable accidentally came off or if I booted without one disk
by mistake, my arrays are dead. This looks too restrictive. I must be
wrong in my conclusion. Please help me see this. Is there a add with
assume clean?
Anyway, there is no point in rebuilding (or adding) it after it failed
this miserably (has 17K reallocated event count, whatever that means) .
I will let the array be degraded until I find a replacement.
I thought write-intent bitmap was not a good idea. May be I did not
research enough. This brings me to the next (probably more important)
question. How do I replace a old drive that has not died without having
to rebuild? If I did a dd image xfer will it accept
the replacement?
Ramesh
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