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Re: ext3 fsck question


On Fri, Feb 15, 2002 at 11:56:38AM +0000, mb/ext3 dcs qmul ac uk wrote:
> After our big ext3 file server crashes, I notice the fsck spends some time
> replaying the journals (about 5-10 mins for all volumes on the server in
> question). I guess it must do this should you want to mount the volumes as
> ext2.

Yes, but 5--10 minutes is a long time.  How many volumes are there?
How large are the journals?  Can you not parallelise the fscks a bit?

> My question--is it (theoretically) possible to tell fsck only to replay
> half-finished and to knock out incomplete transactions from the journals,
> leaving the kernel to replay the good ones in its own time, possibly
> reducing downtime by a few minutes? Or might this break assumptions the
> kernel code makes? Or is it totally impossible and ridiculous? :)

Incomplete transactions are always ignored completely, both by kernel
and e2fsck recovery.  The replay is _always_ going to get done,
because if e2fsck doesn't do it, then the kernel will do exactly the
same thing when you try to mount the filesystems.  The kernel and
e2fsprogs actually share the same recovery.c file for that.

Unless Something Weird is happening, doing the recovery in fsck should
be better because you'll be able to parallelise the recovery on
different disks.  Using kernel recovery, recovery happens at mount
time, and mounts are typically done sequentially.


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