Mailing List Archive

>NFS performance issue on Xen virtual machine
>
>
> From: CamZie <camzie@protonmail.com>
>
> We are using NFS storage mount on our servers and we have noticed the
> difference with the write performance
>

It has been decades since I've used NFS and have never used Xen with NFS,
but I distinctly recall that CPU latency can be a huge problem with
performance.

The one instance I recall was that I ran 4 cpu-intensive processes on a
4-cpu nfs server, and the context switching time of the kernel caused all
clients (dozens to hundreds) to become significantly (10x?) slower. Running
just 1 cpu-intensive process still noticeably degraded the server's
performance.

I would suggest making sure that all the CPUs are idle, perhaps test with
more cores? (i.e. more than 1)

In general NFS is very very latency sensitive. TCP might help with
throughput (reading one large file) as it's been known to help with far
away (25 ms) servers, but for transactional cost (i.e.
open/write/close/stat) lots of files, it shouldn't.

- Kevin