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Re: Linux filesystems was [Re: Debian cd supporting ext4.]

Volkan YAZICI put forth on 7/27/2010 2:04 PM:

> unplugged machine. At boot, I dropped to fsck command line. At command

Were you forced to the command line or did you manually select to go to the
command line?  It sounds like you chose to, not forced to.

> prompt, I manually fiddled around with fsck of xfs to recover the
> unmounted / filesystem, but had no luck. 

Did you read the xfs documentation before embarking on this power loss
experiment?  Or did you it "should just work" regardless of your actions, or
lack of action?  It sounds like you ran xfs_repair on a filesystem in an
inconsistent state and forced changes, which is a no-no.

(I also tried recommendations
> and informative messages supplied by manpages and command
> outputs/warnings.) Also if you would Google, it shouldn't be hard to
> spot similar experiences from other people.

I'm guessing most of them didn't look before taking the XFS leap.

> At NASA, they might have genius technicians; but, IMHO a majority of the
> linux users would want a filesystem to recover without a prompt from the
> user.

So the system wouldn't boot and you were dropped to a prompt.  You manually
fiddled around with fsck of xfs and made no progress.  It would be nice to
have seen all of that at the time.

What were your results when you did this same power yank test with ext2/3,
ReiserFS, and the other filesystems you tested in this way?

>> I'm basically a one man army trying to defeat misinformation WRT XFS
>> and attempt to educate ppl with the correct information.
> I am glad -users ml have you; and I'd be really, really appreaciated if
> somebody having experience and knowledge on fs issues can shed some
> light to our ignorance. I also support the replacement of default fs
> with something that is much more recent. From this point of view, XFS is
> a superior alternative. You are totally right with your claims about its
> advantages over other alternatives. But as you can see, people still
> complain about XFS's sensitivity to power failures. Assuming a majority
> of your users aren't behind a UPS, you can sell/ship your product with
> such a default filesystem choice. But as you said, there are no
> published concrete benchmarks about this issue. It is all what people
> claim in the mailing lists. If you would share some of your findings
> about "Power Failures and XFS" to convince us, I'm sure most of us will
> be happy to advocate XFS's this achievement.

I've tried to dig up accurate accounts of the power loss corruption issue post
2007 (when it was supposed to have been fixed) a few times but couldn't find
anything concrete enough to be worth referencing.  I freely admit I've done no
power loss testing of XFS myself.  This probably has to do with the fact that
I'm a firm believer in orderly shutdowns and redundant power, and that I don't
really have any test systems available.  I'll ask around on the XFS list and
see what folks have to say.

I'm somewhat interested in seeing where BTRFS is in 2-3 years.  It may be
stable enough for production by then, and should be as fast or faster than XFS
on some workloads.  Maybe it'll even handle sudden power loss gracefully. :)


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