Marc Haber wrote:
> (1)
> How do I tell the system that a failed disk has been replaced? If a
> spare disk has been started to be used, can I instruct the system to
> go back to the original disk and to set the spare free again? How do I
> have the system reconstruct the array on a replaced disk? In the
> optimal case, I'd have expected the system to notice that the failed
> disk is back and partitioned as expected, to reonstruct on the "new"
> disk and to set the spare disk free (hey, some people are really
> stingy and use slower disks from the spare parts rack as spare disks
> in RAID installations).
If you are running in degraded mode (as you were after the reboot),
[your prompt]#raidhotadd /dev/md0 /dev/sdc6
will put /dev/sdc6 back in the array (and start resync).
If you then
[your prompt]#raidhotadd /dev/md0 /dev/sdb5
then /dev/sdb5 will be the new spare. To get /dev/sdd6 to become the
spare disk again, run (wait for the resync of /dev/sdc6 to finish before
doing this...) run:
[your prompt]#raidsetfaulty /dev/md0 /dev/sdd6
then remove /dev/sdd6 from the array (removing it will start resync
again...):
[your prompt]#raidhotremove /dev/md0 /dev/sdd6
and put it back in again as a spare:
[your prompt]#raidhotadd /dev/md0 /dev/sdd6
I have been having some trouble with raidsetfaulty though... it would
report an io error (but /proc/mdstat would show the partition as faulty)
and then raidhotremove wouldn't remove the failed partition from the
array (disk busy!) - I would have to reboot to get it out!
> 2)
> What happened on the second disk "failure" when the system became
> unuseable? Isn't it RAID's purpose to keep such things from happening?
> I'd have expected the kernel to notice that the disk is dead for good
> and to stop trying to access it over and over. It worked the first
> time!
If I remember from another time this was asked, that's the SCSI layer
trying _very_ hard to get some answer from your disconnected disk...
Cheers,
Leandro
