[Linux-cluster] optimising DLM speed?
ajb2 at mssl.ucl.ac.uk
Tue Feb 15 20:45:09 UTC 2011
> It would be really interesting how long the described backup takes
when the gfs2 filesystem is mounted exclusively on one node without locking.
The 2 million inode system backs up in about 30 minutes when mounted
lock_nolock (0 file incremental backup using bacula)
> For me it looks like you're facing a similar problem with gfs2 that
has been worked around with gfs by introducing the glock_purge
functionality that leads to a much smaller glock->dlm->hashtable and
makes backups and the like much faster.
Quite likely. Backup performance under GFS2 is slightly worse than with
GFS. "ls -l" in a directory is _significantly_ worse and can take up to
4 minutes for a directory with 4000 files onboard (Remember: This is
with the GFS2 filesystem mounted lock_dlm on one node only!)
Compounding matters, we have a network /home - mounted on the
fileservers and NFSv3 exported to ~150 RHEL5 desktops (Lots of small
files, LOTS of random access).
KDE, Openoffice, Thunderbird, Mozilla are all pretty lock/cachefile
happy and hit the network /home export fairly hard, so when there's a
performance issue the users get pretty noisy.
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