Hi Sam,
On 5/17/20 9:55 AM, Sam Hurst wrote:
Hi Phil,
[trim /]
My complete mdadm -E output:
sosh@toothless:/$ sudo mdadm -E /dev/sda /dev/sdb /dev/sdc /dev/sdd
/dev/sdf /dev/sdg /dev/sdh
/dev/sda:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : f3667bf3:e2b718c2:22cbea68:428ea6ca
Name : toothless:WDRAID
Creation Time : Sat Oct 22 10:52:47 2016
Raid Level : raid6
Raid Devices : 7
Avail Dev Size : 5860271024 (2794.39 GiB 3000.46 GB)
Array Size : 14650675200 (13971.97 GiB 15002.29 GB)
Used Dev Size : 5860270080 (2794.39 GiB 3000.46 GB)
Data Offset : 262144 sectors
Super Offset : 8 sectors
Unused Space : before=262064 sectors, after=944 sectors
State : clean
Device UUID : 08c24be4:d352cbb0:edd50ba7:3a70e02e
Internal Bitmap : 8 sectors from superblock
Update Time : Sat May 2 09:49:27 2020
Bad Block Log : 512 entries available at offset 24 sectors
Checksum : b1df527c - correct
Events : 2687251
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 0
Array State : AAAAAAA ('A' == active, '.' == missing, 'R' == replacing)
[trim /]
So I've tried all six permutations of the devices showing as "spare"
at the end and I can never get a sensible filesystem out when I do a
--create.
Does anyone have any other ideas, or can offer some wisdom into what
to do next? Otherwise I'm writing a shell script to test all 5040
permutations...
It isn't just order that matters. You must get the right data offset
and chunk size. Defaults have changed over the years, and offsets
typically change (+/- 1 chunk) during reshapes.
You'll probably have to manually specify this stuff. Be sure to use
the latest released version of mdadm, even if you have to compile it
yourself.
If your data offsets are at least a couple megabytes, consider
partitioning these disks at the same time as you reconstruct--simply
adjust the data offset for the start sector of the partition. This
will avoid future issues with stupid mobos. (You aren't the first to
suffer from this.)
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).
Your math is wrong. Or rather, you are using the bogus power-of-ten
definition of "MB" that disk manufacturers use to deliver less space.
Use 128MB. Or better, specify "262144s".
I generally recommend using fsck -n to verify a combination, not mount.
But that's because I generally don't bother with overlays. (And why I
get away with it...)
Apologies that it's taken a while to respond to your mail, I just
haven't had much time to look at this during the week.
No worries.
Phil
