EXT3 on raid with external journal...
M K
maheshext3 at yahoo.com
Mon May 24 19:51:01 UTC 2004
Kurt, was there any consensus on this thread?
I am running tests on the same configuration (ext3 on
RAID, with external journal)- are there any particular
tests that you had run? I could run it on my systems
too and post the results in the mailing list.
--- Kurt Fitzner <kfitzner at excelcia.org> wrote:
> Matt Bernstein wrote:
> > On Apr 13 Kurt Fitzner wrote:
> >
> > There could be metadata which is only in the
> journal, so failure probably
> > means reboot + full fsck, so you may as well use
> ext2 if your machine
> > doesn't otherwise crash.
> >
> > Far preferable, I think, would be to put your
> journal on a RAID 1 pair.
>
> I would like to think that if the ext3 driver
> encountered an error
> writing to the journal, that it would then skip the
> journal and write
> straight to the device - reverting to ext2 behavior.
> There should never
> be any loss of data (meta or otherwise) upon the
> failure of a journal
> device. That is, unless the failure of the
> journaling device coincides
> with a power failure. That is:
>
> 1) Failure of journaling device
> 2) Attempted write of metadata to journal device
> 3) Power failure before ext3 gives up on the
> journaling device
>
> In that scenario, the ramification is the array
> requiring a full fsck.
> The benefit of running the journal on an external
> device would far
> outweigh the cost of a full fsck in the unlikely
> event the above happens.
>
> I need to know, though, what exactly is the behavior
> of ext3 in the
> following situations:
> - At system startup if there is a failure to
> "mount" an external journal
> - During operation if the external journal device
> fails.
>
> Does ext3 then revert to non-journaled (ext2)
> behavior in those instances?
>
> -
>
>
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