Re: NFS client renders system unusable

[Sarton O'Brien <sobrien%roguewrt.org@localhost>]

Michael van Elst wrote:
> pitney.brad%googlemail.com@localhost ("Brad Pitney") writes:
>
>   
> > On Sat, Mar 15, 2008 at 5:39 AM, Sarton O'Brien 
> > <bsd-xen%roguewrt.org@localhost> wrote:
> >     
> > >  >> yp_order: clnt_call: RPC: Unable to send; errno = No buffer space
> > >  >> available
> > >  large amount of connections ... all those p2p connections would equate
> > >  to nfs client conections.
> > >       
>
> I doubt that each client connection corresponds to one NFS connection.
> There should be only one connection per NFS _mount_.
>
>   

Ok, I guess I was trying to imply that there would at least be a high 
level of access but low amount of data actually being transfered. I have 
no idea how nfs truly works.

> > Strange, when my NFS server goes away (maybe I've updated it and
> > rebooted), my NFS clients just stall and wait for the server to come
> > back, once it does, just resume as if nothing happened with exception
> > of a few messages like this:
> > Mar 13 00:13:44 nfs-client /netbsd: nfs server
> > nfs-server:/media/data/netbsd/current/obj: not responding
> >     
>
> I would guess that when the NFS connection stalls his application
> just piles up connections. The number of open but waiting connection
> grows beyond bounds and this is eating the (network) buffer space so
> that finally even the single NFS connection fails due to lack
> of memory.
>
> The answer is to limit the number of open connections in his
> application or if there is already a limit, to provide the
> buffer resources necessary. With NetBSD this is the
> kern.mbuf.nmbclusters value and maybe vm.nkmempages too.
>
>   


Yeah was inclined to think there would be a sysctl for something like 
this, I'll definitely have a look.

The client was doing this even when the server was available but 
hopefully I can tweak the required resource to handle the required 
connections. Thanks for the pointer.

Sarton