Re: ffs snapshots patch

[Juergen Hannken-Illjes <hannken%eis.cs.tu-bs.de@localhost>]

On Fri, Apr 29, 2011 at 01:48:39PM +0200, Manuel Bouyer wrote:
> With your last changes, things are much better now:
> /usr/bin/time fssconfig fss0 /home /home/snaps/snap0
>       149.85 real         0.00 user         1.16 sys
> /home: suspended 0.040 sec, redo 0 of 2556
> /usr/bin/time fssconfig fss1 /home /home/snaps/snap1
>       227.49 real         0.00 user         1.90 sys
> /home: suspended 0.040 sec, redo 0 of 2556
> /usr/bin/time fssconfig fss2 /home /home/snaps/snap2
>       263.58 real         0.00 user         2.97 sys
> /home: suspended 0.040 sec, redo 0 of 2556
> /usr/bin/time fssconfig fss3 /home /home/snaps/snap3
>       353.23 real         0.00 user         3.88 sys
> /home: suspended 0.040 sec, redo 0 of 2556
> 
> Taking a snapshot will still probably require a lot of time on
> large filesystems with a dozen snapshots, but at last the server
> won't hang for a long time.
> thanks !

Not really.  Any thread ending up in ffs_copyonwrite() or ffs_snapblkfree()
will block.  If this server runs NFS it could be possible that all NFS
server threads block.

-- 
Juergen Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig 
(Germany)