Thank you very much.
I have other question, about data lose on crash/power cut.
Is it possible to make it not more then in other file systems, if open
the important file with O_SYNC flag, or use fsync and sync functions?
Thanks,
Semion.
-----Original Message-----
From: Eric Sandeen [mailto:sandeen@xxxxxxxxxxx]
Sent: Thursday, April 05, 2007 7:07 PM
To: Zak, Semion
Cc: xfs@xxxxxxxxxxx
Subject: Re: XFS Resiliency to the disk errors.
Zak, Semion wrote:
> Hi,
>
> We are studying possibility to use XFS with cheap (not too reliable)
> discs, so we have some questions:
>
> What in XFS is done to survive the disk errors (bad sectors)?
> I know about superblock duplication in every AG. What else?
>
> What is XFS behavior in case of the disk errors (panic/no
> mount/partial data access)?
generally metadata IO errors or bad magic found in metadata will shut
down the filesystem gracefully if it can.
IO errors on data will just be IO errors.
> What could be done to restore?
xfsdump/xfsrestore I suppose
> If zero bad sector/dump to other device/format/restore will help?
Well, you can't make data out of nothing.
you could dd off the junk drive, zeroing out unreadable sectors, point
xfs_repair at it and hope for the best. Which, depending on the
problem, could wind up not being very good.
If you want to know how to recover from disaster, it sounds like perhaps
your data is important enough that you should not plan for failure, but
rather find a way to avoid it?
Seems to me the only way I'd want to put drives which are expected to
fail regularly into a product is if the recovery method of "replace the
disk and re-image the appliance" was acceptable, but that's just me.
:)
-Eric
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