On Mon, 13 Aug 2012 18:14:30 +0200 "Sam Clark" <sclark_77@xxxxxxxxxxx> wrote: > Thanks Neil, really appreciate the assistance. > > Would love to give that a try - at least to catch the data that has changed > since last backup, however I don't know the chunk size. I created the array > so long ago, and of course didn't document anything. I would guess they are > 64K, but not sure. Is there any way to check from the disks themselves? > > I've captured the 128K chunks as follows - hope it's correct: > > I got the disk size in Bytes from fdisk -l, and subtracted 131072.. then > ran: > sam@nas:~$ sudo dd if=/dev/sd[b-f] of=test.128k bs=1 skip=xxx count=128k, > The 5 files are attached. > > The disk sizes are as follows: > sam@nas:~$ sudo blockdev --getsize /dev/sd[b-f] > sdb: 2930277168 > sdc: 2930277168 > sdd: 2930277168 > sde: 2930277168 > sdf: 3907029168 > Unfortunately the metadata doesn't contain any trace of the the reshape position, so we'll make do with 11.4% The following script will assemble the array read-only. You can then try "fsck -n /dev/md_restore" to see if it is credible. Then try to mount it. Most of the details I'm confident of. 'chunk' is probably right, but there is no way to know for sure until you have access to your data. If you try changing it you'll need to also change reshape to be an appropriate multiple of it. 'reshape' is approximately 11.4% of the array. Maybe try other suitable multiples. 'devs' is probably wrong. I chose that order because the metadata seems to suggest that order - yes, with sdf in the middle. Maybe you know better. You can try different orders until it seems to work. Everything else should be correct. component_size is definitely correct, I found that in the metadata. 'layout' is the default and is hardly ever changed. As it assembles read-only, there is no risk in getting it wrong, changing some values and trying again. The script disassembles and old array before creating the new. good luck. NeilBrown # Script to try to assemble a RAID5 which got it's metadata corrupted # in the middle of a reshape (ouch). # We assemble as externally-managed-metadata in read-only mode # by writing magic values to sysfs. # devices in correct order. devs='sdb sdd sdf sde sdc' # number of devices, both before and after reshape before=4 after=5 # reshape position as sectors per array. It must be a multiple # of one stripe, so chunk*old_data_disks*new_data_disks # This number is 0.114 * 2930276992 * 3, rounded up to # a multiple of 128*3*4. Other multiples could be tried. reshape=1002155520 # array parameters level=raid5 chunk=65536 layout=2 component_size=2930276992 # always creates /dev/md_restore mdadm -S /dev/md_restore echo md_restore > /sys/module/md_mod/parameters/new_array cd /sys/class/block/md_restore/md echo external:readonly > metadata_version echo $level > level echo $chunk > chunk_size echo $component_size > component_size echo 2 > layout echo $before > raid_disks echo $reshape > reshape_position echo $after > raid_disks slot=0 for i in $devs do cat /sys/class/block/$i/dev > new_dev echo 0 > dev-$i/offset echo $component_size > dev-$i/size echo insync > dev-$i/state echo $slot > dev-$i/slot slot=$[slot+1] done echo readonly > array_state grep md_restore /proc/partitions
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