[Linux-cluster] GFS2 metadata performance

Valeriu Mutu vmutu at pcbi.upenn.edu
Wed Mar 23 05:34:21 UTC 2011

Hi Steve,

Thanks for the reply.

On Mon, Mar 21, 2011 at 11:11:31AM +0000, Steven Whitehouse wrote:
> > Note that I've used the same setup for the GFS2 and ext3 tests: same machine, same networking config, same storage array (which is not used by anything else).
> > I also confirmed using "pingpong" [2] that I get a rate of about 4K locks/sec on this particular node against GFS2.
> > 
> The pingpong test does not test metadata performance.

I didn't say pingpong tests/measures metadata performance. I know it measures the _lock rate_, but wasn't sure how the lock rate impacts the metadata performance if any.

> There are a number of variables which you don't mention, but which are
> important for the test results. Firstly, what kind of storage are you
> using? 

I used an idle iSCSI Equallogic PS6500 storage array (48 disks, SATA, 7.2K RPM, 1TB each). It is configured as RAID-50. It is connected to the SAN switch via 4 1gigE links. By idle I mean it was not being used by anything at that time. Also, the VM (on which the test were run) is connected to the SAN switch via a single 1gigE link. MTU was set to 1500bytes due to problems with a 9000bytes MTU.

> Secondly, was this lock_dlm or lock_nolock? 
I've explicitly specified "lock_dlm" as the locking protocol when I created the shared GFS2 filesystem:

> Also was there any memory pressure while the tests were running? 
This VM is mostly idle, i.e. there's almost nothing running on it. It has 2Gb of RAM configured.

>Was noatime set on the filesystem (or indeed, other mount options)?
"noatime" was not set. This is how it's mounted:
/dev/mapper/Gfs2BenchmarksVG-gfs2benchLV on /gfs2bench type gfs2 (rw,hostdata=jid=0:id=196609:first=1)

You've mentioned that you are using other tools to measure the metadata performance of a given filesystem. What tools are those? Also, what numbers have you seen in your benchmarks when it comes to GFS2's metadata performance?

Valeriu Mutu

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