[Lustre-discuss] Geographic cluster

[Brian J. Murrell]

On Tue, 2009-08-11 at 07:35 -0400, Mag Gam wrote:
> How does this replication feature compare to rsync in performance and
> ease of use?

I don't know the details of our replication feature, but I understand
the concepts at a high level.  The major difference between the
replication feature and rsync will be that the replication service will
be "fed" the changes on the filesystem by Lustre rather than it having
to periodically scan the entire filesystem trying to find the changes.
That's a huge win in terms of both time and resources.  Rsync becomes
unusable with very large filesystem due to both the time and memory
required.

It's entirely feasible that rsync could be used as a/the transport for
a/the replication feature as rsync can be given a list of files to
operate on rather than scanning a filesystem.  Whether that's what our
replication feature does or not, I don't know.

All of this is made possible by another upcoming feature, which is
changelogs.  Changelogs is a cool feature in and of itself.  In fact I
*really* wish I could get this same feature out of the more simple,
single disk filesystems, like ext3/4 as another really useful tool for
it is backups (which I suppose is just another flavour of replication,
albeit with an intentional delay).

b.

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