[Linux-cluster] GFS Tunables

[Steffen Plotner]

> -----Original Message-----
> From: linux-cluster-bounces at redhat.com 
> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Gordan Bobic
> Sent: Thursday, October 16, 2008 4:48 PM
> To: linux clustering
> Subject: Re: [Linux-cluster] GFS Tunables
> 
> 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..

> Gordan
> 
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