In testing this some more, I've determined that (always with this
raid10.c patch, sometimes without) the kernel is not recognizing
marked-faulty drives when they're added back to the array. It appears
to be some bit that is flagged and (I assume) normally cleared when that
drive is re-added as an array member.
If I zero the device (I'm assuming it's the wiping of the mdadm
superblock), it will be marked upon issuing 'mdadm /dev/md0 -a
/dev/dm-0' as "spare" instead of "faulty-spare". This behaviour has
been erratic for a while, and I'm not sure if I'm seeing a bug or if I
am working under the wrong presumption with inappropriate actions on my
part.
When a drive is either manually marked "failed" or is automatically
tagged during a failure, is the expected user action to zero the
(original or replacement) drive before doing an 'add'? Should the
kernel recognize that the drive was removed, and that the 'add' should
clear any "faulty" or "failed" state?
/eli
PS - In the process of figuring out when this occurs and how to work
around it, I just hacked up this shell script that takes care of
removing the device from the array, zeroing it, re-reading/scanning the
disk and adding it back in, depending on the function that is called.
Eli Stair wrote:
Thanks Neil,
I just gave this patched module a shot on four systems. So far, I
haven't seen the device number inappropriately increment, though as per
a mail I sent a short while ago that seemed remedied by using the 1.2
superblock, for some reason. However, it appears to have introduced a
new issue, and another is unresolved by it:
// BUG 1
The single-command syntax to fail and remove a drive is still failing, I
do not know if this is somehow contributing to the further (new) issues
below:
[root@gtmp06 tmp]# mdadm /dev/md0 --fail /dev/dm-0 --remove /dev/dm-0
mdadm: set /dev/dm-0 faulty in /dev/md0
mdadm: hot remove failed for /dev/dm-0: Device or resource busy
[root@gtmp06 tmp]# mdadm /dev/md0 --remove /dev/dm-0
mdadm: hot removed /dev/dm-0
// BUG 2
Now, upon adding or re-adding a "fail...remove"'d drive, it is not used
for resync. I realized previously that added drives weren't re-synced
until the existing array build was done, then they were grabbed. This
however is a clean/active array that is rejecting the drive.
I've performed this identically on both a clean & active array, as well
as a newly-created (resync'ing) array, to the same effect. Even after
rebuild or reboot, the removed drive isn't taken back and remains listed
as a "faulty spare", with dmesg indicating that it is "non-fresh".
// DMESG:
md: kicking non-fresh dm-0 from array!
// ARRAY status 'mdadm -D /dev/md0'
State : active, degraded
Active Devices : 13
Working Devices : 13
Failed Devices : 1
Spare Devices : 0
Layout : near=1, offset=2
Chunk Size : 512K
Name : 0
UUID : 05c2faf4:facfcad3:ba33b140:100f428a
Events : 22
Number Major Minor RaidDevice State
0 253 1 0 active sync /dev/dm-1
1 253 2 1 active sync /dev/dm-2
2 253 5 2 active sync /dev/dm-5
3 253 4 3 active sync /dev/dm-4
4 253 6 4 active sync /dev/dm-6
5 253 3 5 active sync /dev/dm-3
6 253 13 6 active sync /dev/dm-13
7 0 0 7 removed
8 253 7 8 active sync /dev/dm-7
9 253 8 9 active sync /dev/dm-8
10 253 9 10 active sync /dev/dm-9
11 253 11 11 active sync /dev/dm-11
12 253 10 12 active sync /dev/dm-10
13 253 12 13 active sync /dev/dm-12
7 253 0 - faulty spare /dev/dm-0
Let me know what more I can do to help track this down. I'm reverting
this patch, since it is behaving less-well than before. Will be happy
to try others.
Attached are typescript of the drive remove/add sessions and all output.
/eli
Neil Brown wrote:
> On Friday October 6, estair@xxxxxxx wrote:
> >
> > This patch has resolved the immediate issue I was having on 2.6.18
with
> > RAID10. Previous to this change, after removing a device from the
array
> > (with mdadm --remove), physically pulling the device and
> > changing/re-inserting, the "Number" of the new device would be
> > incremented on top of the highest-present device in the array.
Now, it
> > resumes its previous place.
> >
> > Does this look to be 'correct' output for a 14-drive array, which
dev 8
> > was failed/removed from then "add"'ed? I'm trying to determine
why the
> > device doesn't get pulled back into the active configuration and
> > re-synced. Any comments?
>
> Does this patch help?
>
>
>
> Fix count of degraded drives in raid10.
>
>
> Signed-off-by: Neil Brown <neilb@xxxxxxx>
>
> ### Diffstat output
> ./drivers/md/raid10.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff .prev/drivers/md/raid10.c ./drivers/md/raid10.c
> --- .prev/drivers/md/raid10.c 2006-10-09 14:18:00.000000000 +1000
> +++ ./drivers/md/raid10.c 2006-10-05 20:10:07.000000000 +1000
> @@ -2079,7 +2079,7 @@ static int run(mddev_t *mddev)
> disk = conf->mirrors + i;
>
> if (!disk->rdev ||
> - !test_bit(In_sync, &rdev->flags)) {
> + !test_bit(In_sync, &disk->rdev->flags)) {
> disk->head_position = 0;
> mddev->degraded++;
> }
>
>
> NeilBrown
>
#!/bin/sh
MODE=$1
ARRAY=$2
DRIVE=$3
alias logger="logger -s -t mdadm_replace"
function DISK_REMOVE {
mdadm -D $ARRAY | grep -E "${DRIVE}$" > /dev/null
MD_DEV_PRESENT="$?"
if [ "$MD_DEV_PRESENT" == "0" ] ; then
echo "// SETTING DRIVE($DRIVE) STATE TO FAULTY "
echo mdadm $ARRAY -f $DRIVE
mdadm $ARRAY -f $DRIVE
sleep 5
echo "// REMOVING DRIVE($DRIVE) FROM ARRAY($ARRAY) "
echo mdadm $ARRAY -r $DRIVE
mdadm $ARRAY -r $DRIVE
MD_DEV_REMOVE="$?"
if [ "$MD_DEV_REMOVE" != "0" ] ; then
echo "// DEVICE ($DRIVE) FAILED TO REMOVE, EXITING UNCLEANLY! "
exit 1
fi
else
echo "// DEVICE ($DRIVE) NOT LISTED, EXITING (PERHAPS REMOVED ALREADY...) "
return 1
fi
} #/FUNCTION DISK_REMOVE
function DISK_READMIT {
echo "// ZEROING DRIVE BEFORE ADMITTING BACK TO ARRAY "
# set 1MB blocksize for 'dd'
BS="1048576"
# get blockdev size in bytes:
DISK_BYTES=`fdisk -l ${DRIVE} 2>/dev/null | grep bytes | head -1 | awk '{print $5}'`
# calculate for DD, to write at offset 64MB from the end of device -> end of device
(( DISK_BYTES_OFFSET=( $DISK_BYTES / $BS ) - 64 ))
# zero 64MB at start of drive
dd if=/dev/zero of=${DRIVE} bs=1M count=64
DD_ERR=$?
# check and make sure we are writing to the drive, else exit with an error
if [ "${DD_ERR}" != "0" ] ; then
echo "COULD NOT ZERO DEVICE ${DRIVE}, EXITING WITH ERROR ${DD_ERR} "
exit 1
fi
# zero drive starting at offset 64MB from end until it hits the wall
dd if=/dev/zero of=${DRIVE} bs=1M seek=$DISK_BYTES_OFFSET
# hackey-like reload of device now that it's been b0rked:
echo "// RE-LOADING DRIVE BY KERNEL "
MASTER=`basename $DRIVE`
for SLAVE in /sys/block/$MASTER/slaves/* ; do
#echo "SLAVE is $SLAVE "
RDEV=`basename $SLAVE`
echo 1 > $SLAVE/device/rescan
sleep 1
blockdev --rereadpt /dev/$RDEV >/dev/null 2>&1
done
blockdev --rereadpt $DRIVE >/dev/null 2>&1
# sleep a few to let udev/kernel catch up
sleep 10
# add device back to array now:
echo "// mdadm $ARRAY -a $DRIVE"
mdadm $ARRAY -a $DRIVE
MD_ADD_ERR="$?"
if [ "${MD_ADD_ERR}" != "0" ] ; then
echo "COULD NOT ADD DEVICE($DRIVE) BACK TO ARRAY($ARRAY), EXITING WITH ERROR ${DD_ERR} "
exit 1
fi
# array now has the replacement drive. show status and exit:
echo -e "\n#### ARRAY $ARRAY STATUS: " | logger
cat /proc/mdstat | logger
echo -e "\n#### DEVICE $DRIVE STATUS: " | logger
mdadm --examine $DRIVE | logger
exit 0
} #/FUNCTION DISK_READMIT
### END SETUP.
### START PROGRAM FLOW:
if [[ (( x"${ARRAY}" == "x" )) && (( x"${DRIVE}" == "x" )) ]] ; then
### necessary input vals not defined, exit.
echo "VALUES NOT SET "
exit 1
else
### ALL CLEAR, run program
# function
$MODE
fi
