[TriLUG] NAS box

[Magnus Hedemark]

On Mon, 3 May 2004, John Reuning wrote:

> I'm not sure I understand.  I thought that netapp filers performed several
> times better than Linux nfs servers, even in a 1500 mtu environment --
> clients on 100 Mb links, filer on either a copper or fibre Gb link.

Part of it is marketing material, part of it is hardware, and part of it 
is really excellent tuning.  You can drop an out-of-the-box Linux system 
on your LAN with lots of disk and have it serve NFS.  But to get 
respectable performance out of it you do need to tune your system.

Jumbo frames, window size, all these things need to be fine tuned for your 
server.  An NFS server configuration could be very different from http or 
dns.

Here is an older article that basically backs up what I said about NFS and 
jumbo frames.  I've proved this out in a production environment with a 
~30TB SAN and the difference can be quite incredible when you take the 
time to tune.

http://www.commsdesign.com/main/1999/03/99032019.htm

Another article (http://www2.rad.com/networks/2003/largemtu/ethjumbo.htm) 
claims "300% increase in throughput combined with a 50% reduction in 
host CPU processing" and "Up to 85% reduction in packet processing."

Your tax dollars at work, with good hard numbers:
http://cdfcaf.fnal.gov/doc/cdfnote_5962/node16.html

Note: "Jumbo frames alone increases the throughput by 35%"
Also: "The single biggest effect was found to be the use of large (32k) 
NFS buffers, with an increase of 40% or more in throughput."

While we're talking about NFS performance tuning in general, don't miss:
http://nfs.sourceforge.net/nfs-howto/performance.html

If you go the gigabit/jumbo frame route don't buy shoddy hardware.  Big 
name brands don't necessarily mean good hardware.  I had a bunch of sun 
servers at one shop that had to go on a different VLAN than the Linux 
servers because the NICs in the Linux servers (Intel e1000 mostly) could 
do jumbo frames, but the Sun branded gigabit NIC's in the Sun Enterprise 
servers could not.