Hi, Köhler
在 2024/4/9 7:31, Sven Köhler 写道:
Hi,
I was shocked to find that upon reboot, my Linux machine was detecting
/dev/sd[abcd] as members of a raid array. It would assign those members to
/dev/md4. It would not run the raid arrays /dev/mdX with members
/dev/sda[abcd]X for X=1,2,3,4 as it usually did for the past couple of years.
My server was probably a unicorn in the sense that it used metadata version
0.90. This version of software RAID metadata is stored at the _end_ of a
partition. In my case, /dev/sda4 would be the last partition on drive
/dev/sda. I confirmed with mdadm --examine that metadata with the identical
UUID would be found on both /dev/sda4 and /dev/sda.
I am trying to reproduce it, but after reboot, md0 started with members
/dev/sd[bc]2 correctly. And mdadm will waring if assemble by 'mdadm -A'.
# mdadm -CR /dev/md0 -l1 -n2 /dev/sd[bc]2 --metadata=0.9
# mdadm -S --scan
# mdadm -A --scan
mdadm: WARNING /dev/sde2 and /dev/sde appear to have very similar
superblocks.
If they are really different, please --zero the superblock on one
If they are the same or overlap, please remove one from the
DEVICE list in mdadm.conf.
mdadm: No arrays found in config file or automatically
Can you tell me how you create and config the RAID?
Here's what I think went wrong: I believe either the kernel or mdadm
(likely the latter) was seeing the metadata at the end of /dev/sda and
ignored the fact that the location of the metadata was actually owned by a
partition (namely /dev/sda4). The same happened for /dev/sd[bcd] and thus I
ended up with /dev/md4 being started with members /dev/sda[abcd] instead of
members /dev/sda[abcd]4.
This behavior started recently. I saw in the logs that I had updated mdadm
but also the Linux kernel. mdadm and an appropriate mdadm.conf is part of
my initcpio. My mdadm.conf lists the arrays with their metadata version and
their UUID.
Starting a RAID array with members /dev/sda[abcd] somehow removed the
partitions of the drives. The partition table would still be present, but
the partitions would disappear from /dev. So /dev/sda[abcd]1-3 were not
visible anymore and thus /dev/md1-3 would not be started.
I strongly believe that mdadm should ignore any metadata - regardless of
the version - that is at a location owned by any of the partitions. While
I'm not 100% sure how to implement that, the following might also work:
first scan the partitions for metadata, then ignore if the parent device
has metadata with a UUID previously found.
I did the right thing and converted my RAID arrays to metadata 1.2, but I'd
like to save other from the adrenaline shock.
Kind Regards,
Sven
.
--
Thanks,
Nan
