NFS veryyyy slow over VPN

[Phil Meyer]

Dr. Michael J. Chudobiak wrote:
> Hi all,
>
> I have a Windows 2000 machine that accesses various local and remote 
> (via a Sonicwall VPN) FC5-server NFS shares, using Windows Services 
> for Unix.
>
> The shares on the local network behave well, but the ones over the 
> remote VPN are slow and tend to freeze Windows Explorer when doing 
> simple things like listing directories. FC5 clients that access the 
> remote VPN share behave better (they pause for a few seconds, but then 
> come back to life).
>
> Does anyone have tips for making NFS work more gracefully for remote 
> Windows clients? (If not, maybe installing Unison on a local FC5 would 
> work better...)
>
> - Mike
>
>
You may wish to play with rsize= and wsize= to a value less than the 
smallest MTU size in the loop (probably 1500).

Export the file system with rsize=1024,wsize=1024 and that should 
eliminate the problem.  However, this will cause a slight performance 
degradation on the local network.

Typically what happens is that the default 8k NFS packet size (wsize and 
rsize default to 8k and may negotiate even larger) is broken up into 
~1500 bytes (less packet header) and have to be reassembled at the 
client.  When the TTL of the pieces expires, the entire 8k needs to be 
retransmitted.  On a local network this rarely happens, but across a WAN 
it is common.

The nfsstat -s command on the server can give some clues.  Look for 
values in the calls line.  Any value above 0 for all but calls on that 
line may indicate an issue.

Also look at netstat -s and pay attention to TCP segments retransmited 
on the NFS server.

Good luck!