On a related note, wouldnt it be more efficient to
have a single dedicated hard drive, with multiple
partitions to store journals - one for each ext3
system?
--- Andreas Dilger <adilger at clusterfs.com>
wrote:> On Apr 20, 2004 23:56 -0500, Vijayan Prabhakaran
> wrote:
> > Is it possible to use a separate journal device
> (one on a separate
> > drive or a partition) shared among more than 1
> Ext3 file systems ?
>
> It is possible now to use an external block device
> for a single filesystem.
> The on-disk format is designed to allow multiple
> filesystems to share the
> same device, but that has never been fully
> implemented.
>
> At one point I had implemented a patch to mount a
> "jbd" filesystem with the
> journal device as the first step of having a shared
> journal device. Having
> the "jbd" device in /etc/fstab (before filesystems
> that use it) allows e2fsck
> to do journal replay on all of the filesystems
> before the journal starts to
> be used, or alternately dumps the journal data to an
> external file for later
> replay (e.g. if block devices are not available when
> e2fsck is run on the
> jbd device). It also allows the jbd code to
> configure the in-core code to
> be ready for external filesystems to connect to it.
> Finally, it also marks
> the block device as in-use so it is less likely that
> it will be overwritten
> accidentally.
>
> See the following email for the (ancient) patch.
> Most of the comments
> and a large fraction of the code in that email are
> still relevant, with
> the exception that all of the UUID handling already
> exists as libblkid
> in e2fsprogs, and it doesn't say what kernel version
> this is for (I'd
> suspect 2.3, but I'm not totally sure. Sadly,
> nobody commented on it
> at the time and it was lost in the mists of
> antiquity.
>
> > Subject: [PATCH][RFC] mountable journal devices
> > To: Ext2 development mailing list
> <ext2-devel at lists.sourceforge.net>
> > Date: Wed, 8 Aug 2001 02:08:23 -0600 (MDT)
>
http://marc.theaimsgroup.com/?l=ext2-devel&m=99725819513803>
> And the thread starting at discusses shared external
> journal devices:
>
https://listman.redhat.com/archives/ext3-users/2001-November/msg00182.html>
> Cheers, Andreas
> --
> Andreas Dilger
> http://sourceforge.net/projects/ext2resize/
> http://www-mddsp.enel.ucalgary.ca/People/adilger/
>
>
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> Ext3-users at redhat.com
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