On 03/12/2010 02:09 PM, Brandon Simmons wrote:
On Fri, Mar 12, 2010 at 1:30 PM, Ric Wheeler<ricwheeler@xxxxxxxxx> wrote:
On 03/12/2010 01:22 PM, Brandon Simmons wrote:
I am using tiobench to test performance of an NFS mounted volume, and
notice that Sequential Reads are much slower than Random Reads. This
isn't the behavior when I run the same test on the disk mounted
locally.
For random reads I'm getting:
50 MB/s over NFS
v.s
384 MB/s when mounted locally
This is in comparison to the benchmark for _Random Reads_, in which I get:
288 MB/s both over NFS _and_ when directly mounted
The other benchmarks seem to be in line with what I would expect, but
I'm fairly new to NFS. Why would sequential reads over NFS be sooo
much slower than random reads over NFS?
I am exporting the volume on the server like this
/export *.internal(no_subtree_check,rw,no_root_squash)
and mounting with this:
mount -o hard,intr,async,noatime,nodiratime,noacl $NFS_SERVER:/export /nfs
Additionally I am doing all this in amazon EC2, exporting an EBS
volume with the XFS file system (redundant, I know).
I have tried using jumbo frames and various other mount options, but
none seem to have much effect.
Thanks for any clues.
Not sure what kind of network you are running the NFS test over so it is
quite hard to figure out why your performance varies so wildly.
Normal NFS testing with a gigabit network between the client and server
would be much closer to 50MB/sec than your 288MB/sec.
Can you try to reproduce this locally with known client and server hardware?
ric
I'm not sure. My servers are EC2 instances in Amazon's cloud computing
service.I am doing the test from an EBS which is a virtual disk
mounted locally on an instance and exported via NFS.
So I don't think I can do any relevant tests locally.
Thanks,
Brandon
The joys of working in the cloud :-)
One possible reason could be that one test is actually going to an NFS
server that is remote, one might be going to one locally (not leaving
the box). I think that you will have to escalate with the Amazon
support/technical people to try and peek under the covers a bit.
ric
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