[Linux-cluster] Backups with GFS and RAM sizing

[David Teigland]

On Fri, Jul 20, 2007 at 01:32:40PM -0400, Danny Wall wrote:
> Thanks for the information. I am a little hesitant about mounting with
> the no_lock option during backups, since the filesystem will be mounted
> on multiple nodes. Currently, only one node writes to the filesystem at
> a time, then the backups run on the other node, but I imagine there
> could still be locking problems between the two.

I was suggesting just having the backup node mount the fs during the
backup, unmounting from all others (assuming they could do without it).

> The /proc/cluster/lock_dlm/drop_count was 50000. After echo the 0, it
> stayed at 0 for a while, and has not gone up yet. I'm not sure what it
> should be, but it did not make a difference on its own. I guess I will
> have to research these.

It's a config setting so it won't change.  A non-zero value limits the
lock caching gfs can do which limits performance.  In the release you're
using I believe you need to set it before mounting for it to have any
impact on the fs.

> I will add a remount at the end of backups to see if that helps any. We
> might be updating later this year, so hopefully this would address #3 at
> that time.

Just to be clear, mount -o remount isn't sufficient to clear out the
unwanted cache, an unmount is required followed by a mount.

Dave