md_d0 is a side-effect of trying to auto-run a conflictingly numbered
device, or non-native host (from a computer with a different hostname)
array.  Otherwise the device is exactly as normal.  If you enumerate
your arrays, even only by UUID and the device name/number you want in
/etc/mdadm.conf it will be obeyed.

Unfortunately I have no clue why your recovery is going so slowly.

Please post:

cat /etc/mdadm.conf
mdadm -Esvv

Possibly also the contents of

dmesg

if it seems even remotely relevant, and also:

for ii in /sys/block/md*/md/sync_speed* ; do \
echo -n "$ii " ; cat $ii ; done

On Thu, Mar 4, 2010 at 9:27 PM, Benjamin Kingston [off-list ref] wrote:

I did some musical HDDs to get my "best" drives to hold a critical md
device, then one failed after a power surge. So I bought a new disk
and added it, then accidentally marked it as failed in the middle of
recovery. I then removed the disk and added it again. I got the
message "/dev/sdd re-added to /dev/md1"

When I do a cat /proc/mdstat the recovery speed is at 55KB/s and
subsequent views of /proc/mdstat show that the speed goes all the way
to 12KB/s or lower. I've since removed and re-added the drive a few
times, but the same thing happens every time and if I leave everything
alone while it resyncs, my CPU usage sky rockets to something like
16.8 23.4 40.5.

Any help would be really appreciated as I don't want to loose the
"good" drive. I know both have good speeds, because I can write at
4MB/s to ext4/luks on md1 and 15MB/s on /dev/sdd with dd.

P.S. could someone also explain to me the difference between md0 and md_d0?
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