[Linux-cluster] Re: Why GFS is so slow? What it is waiting for?
Klaus.Steinberger at physik.uni-muenchen.de
Fri May 9 09:14:01 UTC 2008
> However, it took ages to list the subdirectory on an
> absolute idle cluster node. See below:
> # time ls -la | wc -l
> real 3m5.249s
> user 0m0.628s
> sys 0m5.137s
> There are about 3 minutes spent on somewhere. Does
> anyone have any clue what the system was waiting for?
Did you tune glock's? I found that it's very important for performance of
I'm doing the following tunings currently:
gfs_tool settune /export/data/etp quota_account 0
gfs_tool settune /export/data/etp glock_purge 50
gfs_tool settune /export/data/etp demote_secs 200
gfs_tool settune /export/data/etp statfs_fast 1
Switch off quota off course only if you don't need it. All this tunings have
to be done every time after mounting, so do it in a init.d script running
after GFS mount, and of course do it on every node.
Here is the link to the glock paper:
The glock tuning (glock_purge and demote_secs parameters) definitly solved a
problem we had here with the Tivoli Backup Client. Before it was running for
days and sometimes even did give up. We observed heavy lock traffic.
After changing the glock parameters times for the backup did go down
dramatically, we now can run a Incremental Backup on a 4 TByte filesystem in
under 4 hours. So give it a try.
There is some more tuning, which could be done unfortunately just on creation
of filesystem. The default number of Resource Groups is ways too large for
nowadays TByte Filesystems.
Klaus Steinberger Beschleunigerlaboratorium
Phone: (+49 89)289 14287 Am Coulombwall 6, D-85748 Garching, Germany
FAX: (+49 89)289 14280 EMail: Klaus.Steinberger at Physik.Uni-Muenchen.DE
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