One other question as the badblocks progresses.
 

 It will then recovery both devices in parallel.

How many additional devices can be done at the same time? I presume that I am going to have to replace the 2 failed devices before I try and grow the array by adding 3 additional drives? I so, how many additional drives can be rebuilt concurrently with a grow? Could I add 5 devices and not see too much of a performance hit? Or would it be more sensible to add them one at a time?


YP
 
----- Original Message -----
From: NeilBrown <redacted>
To: jahammonds prost <redacted>
Cc: Linux RAID <redacted>
Sent: Tuesday, 10 April 2012, 19:02
Subject: Re: Failed Array Rebuild advice Please

On Tue, 10 Apr 2012 15:32:44 -0700 (PDT) jahammonds prost
[off-list ref] wrote:

Since I know I did nothing with the temp one drive array when the server was booted (and I don't think that the md code did anything either??) would it be safe to 
 
mdadm --assemble /dev/md0 /dev/sd[a-c]1 /dev/sd[e-h]1 /dev/sd[j-l]1 /dev/sd[n-p]1 --force
 
to let the array come back up and get it running?

Yes.   Though you don't need to exclude the oldest devices.  mdadm will
figure out which ones to use and which ones to avoid.

 
What would then be the correct sequence to replace the 2 failed drives (sdd1 and sdm1) and get the array running fully again?

If you trust that sdd and sdm really are working now, you can

mdadm /dev/md0 --add /dev/sdd1 /dev/sdm1

This will probably start rebuilding just one of the devices. You can check
with
   mdadm -D /dev/md0
which will report "spare building" against one or more devices.
If it is only rebuilding one of them, then

  echo idle > /sys/block/md0/md/sync_action

will cause it to stop and restart the recovery.  It will then recovery both
devices in parallel.

(Next version of mdadm will do this automatically).

NeilBrown

 
 
Thanks for your help.
 
 
YP.
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