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-   -   Check your /etc/default/grub, if you use raid 1. (http://www.linux-archive.org/fedora-user/688628-check-your-etc-default-grub-if-you-use-raid-1-a.html)

Sam Varshavchik 07-29-2012 02:02 PM

Check your /etc/default/grub, if you use raid 1.
 
There's a long standing combination of two bugs: the list of rd.md.uuid boot
parameters generated by anaconda for /etc/default/grub may not include the
raid uuid of non-stock partitions like /home; and although the ramfs
initscript autodiscovers all raid volumes present, sometimes (not always,
I'll estimate 5% of the time) if a uuid is not enumerated in the boot
parameters, one of the drives in the raid 1 volume may not get assembled at
boot.


There's probably a third bug in here: mdmonitor should've mailed me when an
array came up degraded at boot (I suspect that because mdmonitor gets
started so early in the boot process, not all the moving pieces are there
for mail delivery to happen). Eventually, you'll boot again with both drives
in the array somehow, except they'll be out of sync, resulting in massive
corruption. If you're lucky, you'll boot just with the other drive, and
discover that your filesystem's contents are weeks/months out of date, and
maybe you'll be lucky enough to figure out what happen, and switch back to
the other drive and resync. But, not everyone's so lucky.


This first started happening in F16. It took me a while to figure out the
cause for an occasionally raid assembly failure at boot. Fixed it, and
forgot about it. Well, looks like the F17 anaconda brought back the broken
/etc/default/grub, which found its way into my grub.cfg, and I just lost a
full day, cleaning up this mess.


So, if you use raid 1 and upgraded to F17, you may need to fix this before
it's too late: put back the missing uuid into /etc/default/grub, and into
every entry in grub.cfg


Pissed.

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Bruno Wolff III 07-29-2012 02:19 PM

Check your /etc/default/grub, if you use raid 1.
 
On Sun, Jul 29, 2012 at 10:02:00 -0400,
Sam Varshavchik <mrsam@courier-mta.com> wrote:
There's a long standing combination of two bugs: the list of
rd.md.uuid boot parameters generated by anaconda for
/etc/default/grub may not include the raid uuid of non-stock
partitions like /home; and although the ramfs initscript
autodiscovers all raid volumes present, sometimes (not always, I'll
estimate 5% of the time) if a uuid is not enumerated in the boot
parameters, one of the drives in the raid 1 volume may not get
assembled at boot.


My raid info is /etc/mdadm.conf and that is what gets used by dracut when
building an initramfs as far as I can tell.


There's probably a third bug in here: mdmonitor should've mailed me
when an array came up degraded at boot (I suspect that because
mdmonitor gets started so early in the boot process, not all the
moving pieces are there for mail delivery to happen). Eventually,
you'll boot again with both drives in the array somehow, except
they'll be out of sync, resulting in massive corruption. If you're
lucky, you'll boot just with the other drive, and discover that your
filesystem's contents are weeks/months out of date, and maybe you'll
be lucky enough to figure out what happen, and switch back to the
other drive and resync. But, not everyone's so lucky.


That doesn't sound right. You might come up using the incorrect raid member,
but you should come up with two out of sync drives. (Maybe this could happen
with some non-default setups, where the elements aren't labelled.)


There was a recent bug with raid arrays that could result in some elements
failing when shutting down. It doesn't directly corrupt the data though.
There is information about this bug here:
http://neil.brown.name/blog/20120615073245

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