8.04-1 won't boot from degraded raid

Soren Hansen soren at ubuntu.com
Tue Aug 26 15:54:53 UTC 2008

On Tue, Aug 26, 2008 at 10:20:45AM -0500, Michael Hipp wrote:
>>>> But in the meantime ... this is Intrepid. What do I do about the
>>>> "production" Hardy that I is now known to ship with a broken RAID
>>>> implementation?
>>> Just because it doesn't boot without intervention from a degraded
>>> RAID, that doesn't mean it won't carry on when the RAID degrades
>>> right?  Or am I missing the issue?
>> No, you are quite right. I also don't particularly approve of such
>> frivolous usage of the word "broken".
> What word would *you* choose to describe a server that won't boot when
> only one of it's (supposedly redundant) members is down?

Apparantly, I should be calling it a server "that doesn't do what
Michael Hipp expects it to".

> It might help if you were aware that I've been fighting this issue
> with Ubuntu releases ever since the days of 4.10:
> http://ubuntuforums.org/showthread.php?t=15655
> https://bugs.launchpad.net/ubuntu/+source/kernel-package/+bug/12052

Ok, make that: a server "that *still* doesn't do what Michael Hipp
expects it to".

I'm quite happy that the server doesn't boot if my raid array is broken,

Imagine a scenario where the disk controller is flaky. Disk A goes away
while the system is running, and is then out of date. You reboot the
machine (or perhaps it rebooted itself because the flaky controller
short circuited or whatever), and for whatever reason (flaky controller,
remember?), the system boots from disk B instead. The changes to your
filesystem since disk A disappeared away are not there, and new changes
are being written to disk B, and there's no chance of merging the two.
This is what I refer to as "having a very bad day".

There are lots of other scenarios where you really don't want to boot if
your RAID array is not in tip-top shape. If the system is already
running, it knows something about its current state, which disk is the
more trustworthy one, etc. When booting, this is not the case.

I value data over uptime.

> Every time I think it's fixed I seem to learn that it's uh, er, not
> functional once again.

"Not acting in the way you want" is not the same as "not functional".

> (I'm pretty sure it works fine in 6.06 LTS tho it's been a long time
> since I tested it.)

Nope. It's the same.

> I've been installing operating systems on RAID1 for my little LAN
> servers for as long as I can remember. Before Ubuntu it never occurred
> to me that getting a system to boot a RAID1 with a defunct member was
> some rocket science.

True, it's more difficult than it could be. Dustin has been working hard
on getting that fixed in Intepid. 

> Why, pray tell, can't Ubuntu make this Just Work like most every thing
> else in Ubuntu?

"Just Work" in this context means different things to different people.
To me, "Just Work" means that it above all doesn't corrupt my data. To
others, it might mean "start the sucker no matter what, so that I can
get on with my life". Neither is a malfunction, so both options should
be available, but spare me the "broken" and "not functional" babble.

> Would my rant be any better received if I pointed out that this stuff
> has worked just fine in versions of Red Hat and Windows dating back
> almost a decade.

Not in particular, no.

Soren Hansen               | 
Virtualisation specialist  | Ubuntu Server Team
Canonical Ltd.             | http://www.ubuntu.com/
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