[ILUG] tuning NFS over a wireless LAN

[David Malone]

As Padraig mentioned, WiFi has pretty big per-packet overheads: you
pay for two PHY headers, one for the packet and one for the MAC
ACK. In 802.11b that can be an additional 192 or 384us in an overall
cost of ~1400us for 1500 byte 802.11b packet. Naturally, this is
much worse for small packets. I would guess that making sure that
NFS sends big packets whenever possible is important. The large
rsize and wsize should help with this, but you'll still get small
requests followed by large responses - I don't think there is a lot
you can do about this.

If any of your WiFi hardware supports putting two packets in one
MAC frame (the Atheros drivers support this - I think they call it
"fast frames" or somesuch), then that might help a bit. I've never
tested this to see how effective it is.

We have some nice performance improvements to TCP over wireless,
but mainly for the situation where you have multiple wireless
clients. (Which reminds me, it might be worth turning the Linux
frto stuff on, but YMMV).

> One of the uses will be to access a reasonably large library of MP3s,
> fwiw.

I tried this a few years ago - I was using iTunes to read MP3s over
NFS over WiFi - it worked pretty well with an old airport and iBook.

	David.