On 29-05-12 01:09, NeilBrown wrote:
On Tue, 29 May 2012 00:44:55 +0200 Oliver Schinagl<oliver+list@xxxxxxxxxxx>
wrote:
On 05/29/12 00:07, NeilBrown wrote:
On Mon, 28 May 2012 22:50:03 +0200 Oliver Schinagl<oliver+list@xxxxxxxxxxx>
wrote:
Hi list,
I'm sorry if this is the wrong place to start, but I've been quite lost
as to what is going wrong here.
No, you are in exactly the right place!
Pfew :D
I've been having some issues latly with my raid10 array. First some info.
I have three raid10 arrays on my gentoo box on 2 drives using GPT.
I was running 3.2.1 at the time but have 3.4.0 running at the moment.
mdadm - v3.2.5 - 18th May 2012
md0, a 2 far-copies, 1.2 metadata, raid10 array consisting of /dev/sda4
and sdb4.
md1, a 2 offset-copies, 1.2 metadata, raid10 array consisting of
/dev/sda5 and sdb5
md2, a 2 offset-copies, 1.2 metadata, raid10 array consisting of
/dev/sda6 and sdb6
I'm liking the level of detail you are providing - thanks.
The more information provided, the better I always recon!
sd*1 is bios_grub data, sd*2 is 256mb fat for playing with uefi and sd*3
is 8gigs of unused space, may have some version of ubuntu on it and sd*7
for swap.
For all of this, md0 has always worked normally. it is being assembled
from initramfs where a static mdadm lives as such:
/bin/mdadm -A /dev/md0 -R -a md /dev/sda4 /dev/sdb4 || exit 1
In general I wouldn't recommend this. Names of sd devices change when
devices are removed or added, so this is fragile. It may cause the actual
problems you have been experiencing currently.
Yes! Yes yes yes! I know. Kinda offtopic here, but:
I've always used a small 100mb -250mb (or 1gb on my desktop) array using
metadata 0.9 and autodetect. This worked perfectly. /usr, /home etc
where on exotic raid setups (metadata 1.2 etc) but this all just worked
(tm).
Recently Fedora decided booting and /usr was a mess and not long after
udev (i belive not only in gentoo) 'agreed' that /usr and / should be
merged.
With 0.90 autodetect being depreciated by the kernel anyway I decided to
bite the bullit and use my 8gb /usr as combined / and /usr. Now however
I was 'forced' to also use an initramfs to get my raid array going. Long
story short, I just quickly hacked that together as minimally as
possible, as I haven't found any 'clean' way to do
it/documented/recommended way to copy.
It's not only just error-prone, It's also broken. Having a disk missing
or fail, causes kernel panics due to init pre-maturly failing because
mdadm fails at finding /dev/sdb.
If you want to build a simple-as-possible initramfs to assemble you root md
array, I recommend README.initramfs in the mdadm source code.
http://neil.brown.name/git?p=mdadm;a=blob;f=README.initramfs;h=8f9b8ddffb32f1eb3dc087ccda9bc0ff93870a33;hb=HEAD
md1 and md2 are being brought up during boot, md0 holds root, /usr etc
wheras md1 are just for home and data.
The last few weeks md1 and md2 randomly fail to come up properly. md1 or
md2 come up as inactive and one of the two drivers are marked as spares.
(Why as spares? Why won't it try to run the array with a missing drive?)
While this happens, it's completly abitrary whether sda or sdb is being
used. so md1 can be sda5[2](S) and md2 can be sdb5[2](S).
The (S) is a bit misleading here. When an array is 'inactive', all devices
are marked as '(S)', because they are not currently active (nothing is as the
whole array is inactive).
When md1 has sda5[2](S), is sdb5 mentioned for md1 as well, or is it simply
absent. I'm guessing the second.
Yes, i'm 99% sure however it's randomly sda6 or sdb6 that's shown. But
never both. Only if I do mdadm -A /dev/md2 /dev/sda6 /dev/sdb6 (after
stopping md2 first of course).
That makes sense.
This it most likely caused by "mdadm -I" being run by udev on device
discovery. Possibly it is racing with an "mdadm -A" run from a boot script.
Have a look for a udev/rules.d script which run mdadm -I and maybe disable it
and see what happens.
In init.d I find two scripts calling mdadm. /etc/init.d/mdadm only does
monitoring (mdadm --monitor --scan --daemonize) I strongly doubt that
forces any of the assembling? (even though scan is there?)
/etc/init.d/mdraid does some md stuff, but that's not run nor enabled.
BTW, I only start md0 from initramfs, so udev apparently does the rest
(and sucks at it?)
Let's just say it is not yet perfect at it.
Now that you are using mdadm 3.2.5 there is a better chance that it will work
reliably. Is it still failing?
Just booted 5 minutes ago, and yes, only sdb5 shows for md1. mdadm
--stop /dev/md1; mdadm -A /dev/md1 made it come up just fine. I have
removed mdadm (--monitor --scan) from my boot up scripts now and will
keep an eye on this. (It was in the boot runlevel however, don't know if
that was my mistake or not).
When this happens, I mdadm --stop /dev/md1 and /dev/md2, followed
immediatly by mdadm -A /dev/md1 (using mdadm.conf which doesn't even
list the devices. ARRAY /dev/md1 metadata=1.2 UUID=nnn name=host:home).
The arrays come up and work just fine.
What happend today however, is that md2 again does not come up, and
sda6[3](S) shows in /proc/mdadm. However re-assembly of the array fails
and only using mdadm -A /dev/md2 /dev/sda6 /dev/sdb6 shows:
mdadm: device 1 in /dev/md2 has wrong state in superblock, but /dev/sdb6
seems ok
mdadm: /dev/md2 assembled from 0 drives and 2 spares - not enough to
start the array.
/proc/mdadm shows as somewhat expected.
md2 : inactive sda6[3](S) sdb6[2](S)
Only using sdb6 however also fails. I guess because it does not want to
use a spare.
mdadm: failed to RUN_ARRAY /dev/md2: Invalid argument
mdadm: Not enough devices to start the array.
Now the really disturbing part comes from mdadm --examine.
valexia oliver # mdadm --examine /dev/sda6
/dev/sda6:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : nnnn
Name : host:opt (local to host host)
Creation Time : Sun Aug 28 17:46:27 2011
Raid Level : -unknown-
Raid Devices : 0
Avail Dev Size : 456165376 (217.52 GiB 233.56 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
State : active
Device UUID : nnnn
Update Time : Mon May 28 20:52:35 2012
Checksum : ac17255 - correct
Events : 1
Device Role : spare
Array State : ('A' == active, '.' == missing)
sdb6 lists identical content only with the checksum's being correbt,
albeit different and of coruse the Device UUID. Array UUID is of course
identical as is creation time.
Also to note, is that grub2 does mention an 'error: Unsupported RAID
level: -1000000.' which probably relates to the 'Raid Level: -unknown-'.
As to what may have caused this? I have absolutely no idea. I did a
clean shutdown where the arrays get cleanly unmounted. Not 100% sure if
the arrays get --stopped but I would be surprised if they did not.
So I guess is this a md driver bug? Is there anything I can do to
recover my data, which i cannot image it not being?
This is a known bug which has been fixed. You are now running 3.4 so are
safe from it.
Well this strange behavior all stemmed from running 3.2.1. I've only
upgraded to 3.4 to see if that 'fixes' it. (It didn't :( unfortunately).
I think that bug was in 3.3 and 3.2.1 and fixed in 3.4 and some later 3.3.y
and 3.2.y kernels.
The bug would cause an array to be destroyed at shutdown in some unusual
circumstances. Once destroyed you need to re-create.
The -100000 error I'm assuming for now also stems from the meta data
being corrupt, and will probably go away when trying the below tomorrow :)
Correct.
You can recover your data by re-creating the array.
mdadm -C /dev/md2 -l10 -n2 --layout o2 --assume-clean \
-e 1.2 /dev/sda6 /dev/sdb6
Check that I have that right - don't just assume :-)
That looks very similar to what I used to create the array with, except
the assume-clean part. I wonder however, would it not wiser to create
the array using /dev/sda6 missing thus creating a degraded array?
Atleast I'll still have the sdb6 which MAY contain the data also (since
only sda6 'apparently' has wrong state?
That would be a suitable approach - arguably safer. If you feel more
comfortable with it, then that is a strong reason to follow that course.
I have tried that on sda6 but it cannot file a filesystem when trying to
mount md2. This of course is quite scary. I am now slightly doubting if
my chunksize is the same as before, 128k.
I've used the following command.
mdadm -C /dev/md2 -c 128 -l 10 -p o2 --assume-clean -e 1.2 -n 2
--name=opt /dev/sda6 missing
Now I could try the same on sdb6 and hope that does work, but slightly
scared of loosing everything on that partition, it could be possible of
course that sdb6 is the partition that has everything in the 'proper'
order? I will try to losetup sdb6 with an offset and see if that is
mountable.
Also, would it not be possible to mount sdb6 using the correct offset? I
remember raid1 array's could simply be mounted. (with a 2 disk raid10,
from what I understand, atleast 1 disk may be mountable?)
No. That only works with the 'near' layout. You used an 'offset' layout.
So if the chunks of data are 'A B C D E F G H', then the first disk contains
A B C D E F G H
but the second disk contains
B A D C F E H G
so you could mount sda6 if you added an offset with losetup or similar, but
not sdb6.
That's what I ment with atleast 1 disk :) This as asked above, could
also be the other way around, right? sdb6 mountable but sda6 not?
when you have created the array, check that the 'Data Offset' is still
correct, then if it is "fsck -n" the array to ensure everything looks good.
Then you should be back in business.
I should then be able to compare it to md1/sda5 and /dev/sdb5. Since md1
and md2 where created with identical settings, they should be almost the
same when comparing :)
So to summarize, my array went foobar due to an old known bug and the
only way to fix it is to recreate the array, leaving the actual data in
place. The FS _should_ start after 2048 sectors on the disk.
Correct.
This would also be the location for the offset? 2048 *sectorsize (+1)?
NeilBrown
Oliver
NeilBrown
Thanks in advance for reading this.
Oliver
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Thank you so far for your help!
Oliver
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