Separate common journal device

M K maheshext3 at yahoo.com
Thu May 27 19:59:15 UTC 2004


Oh, good point.. BTW,  what should the ideal size of a
journal be ? is there a general guideline to follow ?
I am sort-of a newbie to ext3, any advice on choosing
the journal size would be great!
Thanks in advance,
Mahesh

--- Andreas Dilger <adilger at clusterfs.com> wrote:
> On May 24, 2004  12:45 -0700, M K wrote:
> > 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? 
> 
> No, because then each filesystem would cause seeking
> to its part of the
> journal for each transaction (unless the dedicated
> device was NVRAM).
> In general, the writes to the journal are pure
> overhead unless you
> actually crash so they need to be as efficient as
> possible at write time
> and the complexity at recovery time is much less
> critical.
> 
> Having all of the journal writes for multiple
> filesystems stream to a
> single block device without any seeking is the best.
>  Making a larger
> journal also helps a lot in the performance area,
> but you can't always
> afford to consume so much RAM on a system
> (especially a larger journal
> for each filesystem).
> 
> > --- Andreas Dilger <adilger at clusterfs.com> wrote:
> > > 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.
> 
> 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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