On 17/05/2020 14:55, Sam Hurst wrote:
So I've now tried doing this and sadly haven't really gotten anywhere.
Given the output of mdadm -E, I've specified the chunk size as 512K, and
the data offset as 134MB (given the reported offset of 262144 sectors *
sector size of 512 bytes on the devices).
Given your statement that I could trust the existing superblocks, I
haven't messed around with the order of those and instead I've just been
messing around with the order of the three disks which are unhappy. So
I've been putting sda first (active 0), then sdc (active 1), sdb (active
2), and sdd (active 3). As I said last time, I'm using overlay images to
avoid screwing up the disks. My create command line is as below:
mdadm --create /dev/md1 --chunk=512 --level=6 --assume-clean
--data-offset=134M --raid-devices=7 /dev/mapper/sda /dev/mapper/sdc
/dev/mapper/sdb /dev/mapper/sdd ${UNHAPPY_DISK1} ${UNHAPPY_DISK2}
${UNHAPPY_DISK3}
One other thing which I meant to write on the previous email but forgot,
my test of "is the array sane" is to try and mount the XFS filesystem on
the array. However, each time it just fails to find the filesystem
superblock and is generally unhappy.
Reading the manpage, the only other thing I can see which I could put
into the --create command is the layout of the array, which I'm fairly
sure was left-symmetric because that's what the original RAID 5 array
was according to my backup of the RAID configuration before moving to
RAID 6, but I can't remember what the second parity disk layout was.
And in case it is helpful, the following is what mdadm thinks about the
new array that I try to build.
root@toothless:~# mdadm -D /dev/md1
/dev/md1:
Version : 1.2
Creation Time : Sun May 17 14:38:34 2020
Raid Level : raid6
Array Size : 14650644480 (13971.94 GiB 15002.26 GB)
Used Dev Size : 2930128896 (2794.39 GiB 3000.45 GB)
Raid Devices : 7
Total Devices : 7
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Sun May 17 14:38:34 2020
State : clean
Active Devices : 7
Working Devices : 7
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : bitmap
Name : toothless.local:1 (local to host toothless.local)
UUID : ddf9f835:dc0fdad0:c864d5f5:f70ecbbf
Events : 1
Number Major Minor RaidDevice State
0 253 2 0 active sync /dev/dm-2
1 253 3 1 active sync /dev/dm-3
2 253 0 2 active sync /dev/dm-0
3 253 1 3 active sync /dev/dm-1
4 253 4 4 active sync /dev/dm-4
5 253 6 5 active sync /dev/dm-6
6 253 5 6 active sync /dev/dm-5
-Sam
