On Sun, 2008-03-30 at 14:54 -0500, Wendy Cheng wrote: snip... > In general, GFS backup from Linux side during run time has been a pain, > mostly because of its slowness and the process has to walk thru the > whole filesystem to read every single file that ends up accumulating > non-trivial amount of cached glocks and memory. For a sizable filesystem > (say in TBs range like yours), past experiences have shown that after > backup(s), the filesystem latency can go up to an unacceptable level > unless its glocks are trimmed. There is a tunable specifically written > for this purpose (glock_purge - introduced via RHEL 4.5 ) though. What should I be setting glock_purge to? snip... > The thinking here is to leverage the embedded Netapp copy-on-write > feature to speed up the backup process with reasonable disk space > requirement. The snapshot volume and the cloned lun shouldn't take much > disk space and we can turn on gfs readahead and glock_purge tunables > with minimum interruptions to the original gfs volume. The caveat here > is GFS-mounting the cloned lun - for one, gfs itself at this moment > doesn't allow mounting of multiple devices that have the same filesystem > identifiers (the -t value you use during mkfs time e.g. > "cluster-name:filesystem-name") on the same node - but it can be fixed > (by rewriting the filesystem ID and lock protocol - I will start to test > out the described backup script and a gfs kernel patch next week). Also > as any tape backup from linux host, you should not expect an image of > gfs mountable device (when retrieving from tape) - it is basically a > collection of all files residing on the gfs filesystem when the backup > events take places. > > Will the above serve your need ? Maybe other folks have (other) better > ideas ? This sounds exactly like what I can use - and it's got to be useful for everyone with a NetApp and gfs. Thanks for doing this! Let me know how I can help. Regards, -C -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
