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Re: [Linux-cluster] GFS Tunables



Steffen Plotner wrote:

Kevin Anderson wrote:
On Thu, 2008-10-16 at 21:29 +0100, Gordan Bobic wrote:
Brandon Young wrote:

As for LVM snapshotting ... I am under the impression that those features are unavailable in GFS (and are slated for GFS2?
Which is
not "production ready", yet?) It has certainly occured
to me to try
that feature, if only it were available. Am I
misinformed? Perhaps
I need some more education on how exactly LVM mirroring will help me. I am *attempting* to approximate a traditional backup scheme,
atleast on
this particular filesystem. Am I correct in believing
that I could
snapshot a volume (assuming the feature is available) and run a traditional backup (using, say, rdiff-backup) in a
shorter time than
I can now, where I'm running it straight off a live GFS volume?
You can use CLVM (Cluser aware LVM) and create GFS on top of that volume. You can them use CLVM to take a snapshot of the
block device,
mount it read-only with lock_nolock and back that up. That
should go
at non-clustered FS speeds.

We don't have support for cluster snapshots as of yet even
though it
has been on the todo list for about 5 years now :(.
Joy... My mistake. Sorry I mentioned it.


How about snapshotting at the backend storage device? We usually use
linux as the backed, hand out storage via iscsi and snapshot at the
backend - this eliminates the need for doing snaps at the GFS level - I
agree that if there was snapshotting at the LVM/GFS level we could get a
clean snapshot.... another problem..

The problem with that being that you have your storage system as a single point of failure which rather defeats the point of clustering.

Gordan


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