Hi Miles,

Miles O'Neal wrote on 2/26/2009 2:04 PM:
> P. Larry Nelson said...
> 
> ...
> |I am currently going thru and adding "udp" to all the SL4.7 clients' fstab
> |entries so they will use UDP rather than TCP.
> |
> |My main question is, lacking any explicit protocol designation in the fstab,
> |how can one tell which protocol a client is using?
> 
> You can find the tcp connections using
> 
>    netstat -a | grep nfs

Right, that sort of works.  :-)
If a client *is* using TCP for nfs, then those connections show up.
If a client is using UDP for nfs, then nothing shows up.

> or just run
> 
>    cat /etc/mtab
> 
> to see each mount.

That, like running the 'mount' command, only shows the protocol *if* the
protocol has been explicitly entered in the fstab.

> |And lastly, why wasn't the change documented in the release notes?
> |
> | From what I've gleaned about the two protocols from googling, it appears
> |that TCP has advantages on a lossy network but that's not our scenario.
> |It also is not a stateless protocol, like UDP, so if a server crashes in
> |the middle of a packet transmission, the client will hang and filesystems
> |will need to be unmounted and remounted.  So it would seem UDP is better,
> |at least in our case.
> 
> We found things to be much more robust, and only very slightly
> slower, using tcp.  We had plenty of hangs using udp, but that
> was many kernel revs and other bugs back, so who knows?
> 
> -Miles

Thanks!
- Larry
-- 
P. Larry Nelson (217-244-9855) | Systems/Network Administrator
461 Loomis Lab                 | High Energy Physics Group
1110 W. Green St., Urbana, IL  | Physics Dept., Univ. of Ill.
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