tuning NFS for a write heavy environment

[David A. Bandel]

On Thu, Sep 25, 2008 at 8:47 PM, Lonni J Friedman <netllama at gmail.com> wrote:
> Anyone have any experience tuning NFS (Linux only) for a write
> intensive environment ?
>
> For background:
> I've got a Linux NFS server, serving up /home from a 3 SATA disk
> mdraid RAID5 array (underlying filesystem is XFS).  Alot of developers
> are using this NFS mount for doing builds, so its almost continuously
> under heavy write pressure.   The server usually has a bunch of nfsd
> processes consuming most of the CPU time.

How many nfs mounts are we talking about, and are the developers just
writing files across this mount or are they actually trying to compile
across the mount?

Can you add another _good_ ethernet card (full duplex) to the nfs
server to help distribute the load?

>
> The server itself has a Athlon64X2-6400 (3.2Ghz) CPU, with 2GB of RAM.
>  Its not swapping at all.

Some rambling thoughts:

Why should it swap?  The bottleneck is your network.  That should fill
your buffers pretty good.

I have a school that has 16 computers that nfs boot across a network.
In years past they only had /home mounted and had no problems.  Now
the entire system is mounted that way, but they run remote X, so all
the graphics come across the network.

Not exactly the same, but again, your bottleneck will be the network
-- hope you're not running cheap half-dup cards is all.

Try finding something like ntop and looking at your network load (or
just watch the switch lights at peak load periods to see how many
collisions you're having).

Check to see if your nfs exports are synchronous or async.  Async
isn't as safe, but should give a performance boost as it won't block
the way synchronous does.

Are they all writing to the same files? (file-locking issues?)

Ciao,

David A. Bandel
-- 
Focus on the dream, not the competition.
            - Nemesis Air Racing Team motto