NFS server usage

Charles Swiger cswiger at
Thu Feb 26 13:33:15 PST 2004

On Feb 26, 2004, at 2:30 PM, Michael Conlen wrote:
> Does FreeBSD's NFS implementation allow for caching of documents on 
> the client side, either its self or through the VM system's inactive 
> pages?

Yes to both.  NFS clients typically use something called biod or 
nfsoid, which implements some combination of caching and I/O request 
coalescing in order to reduce the amount of network traffic going to 
the server.

[ Yes, this means that fsync() over NFS isn't guaranteed to actually 
have bits written to disk, at least historically... ]

> The reason I'm asking is that I'm trying to size an NFS server using a 
> few of many similar sites that I hope to cluster. The performance so 
> far has been great, but I'm worried that there's something I'm missing 
> here that will cause the performance/usage to change in a very 
> nonlinear way. Any thoughts on the subject are appreciated.

Well, you are going to be bottlenecked potentially by your network or 
by the maximum I/O rate that your NFS server can sustain.  Your data 
suggests you ought to be able to handle about two orders of magnitude 
more net traffic, if you're over a dedicated 100 Mbs connection between 
server and clients (ie, using a switch), so it's likely that you're 
going to run into limits due to your disks well before then.

You can probably switch to using rsync or some other replication scheme 
instead of NFS if you do run into limits, and keep the files locally if 
need be.


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