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Re: [Condor-users] tuning a file server
- Date: Tue, 02 Aug 2005 00:27:50 +0100
- From: David McBride <dwm@xxxxxxxxxxxx>
- Subject: Re: [Condor-users] tuning a file server
Steffen Grunewald wrote:
some weeks ago, I had to move our file systems (/home and some data) to
another server, equipped with 3ware 9000 cards, and using 8 400GB disks
in RAID5 with hot spare (2.3TB net capacity). To manage the disk space,
I had to switch to Linux kernel 2.6 - and there are indications that this
move caused some problems.
3ware tend to make excellent Linux-compatible RAID solutions, so it is
unlikely to be a RAID-level problem, as your basic read benchmark
I'd suggest also running the 'bonnie++' benchmark on your filesystem to
get a better idea of real-world performance (file creates/erasures,
small loads, etc.)
The file server has to serve 360 VMs in 180 dual-CPU machines, and if
there are lots of small I/O operations, the iowait percentage goes up to
more than 80%! I have never seen that before (the previous server was
almost identical, kernel 2.4, 1.4TB each).
Some important missing information:
* How (if at all) are the fileserver contents exported? NFS?
* What filesystem(s) are you using?
> Now I suspect that the i/o strategies introduced with 2.6 kernels are
> badly configured... are there any suggestions?
The 2.6 IO schedulers tend to _better_ than the 2.4 one. The default is
to use the 'anticipatory' scheduler which tends to be excellent for most
David McBride <dwm@xxxxxxxxxxxx>
Department of Computing, Imperial College, London