*BSD News Article 90181


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: 2 NFS problem
Date: 2 Mar 1997 20:59:58 GMT
Organization: Private BSD site, Dresden
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:36456

kongwah@iss.nus.sg (Wan Kong Wah) wrote:

> I have a freebsd machine which writes VERY slowly to an
> remote NFS directory exported from a DEC server machine.
> A simple cp of 400Kbytes take 4-5 seconds.

That's probably not a very unusual value.  With NFSv2, the server must
ensure the data have been written ``to stable storage'' before it is
allowed to return from the NFS write call.  I've seen rates of 150 or
200 KB/s, but not much more.

For small files, the nfsiod's on the client machine help out of this
dilemma.

With NFSv3, matters are different, since there's an official way to do
asynchronous writes.  Some NFSv2 implementations (like SGI IRIX) are
cheating, and perform async writes even in v2.  This violates the
specs unless the machine can otherwise guarantee the delayed write
will indeed succeed (which requires at least an UPS, plus an operating
system that never crashes).

(FreeBSD offers this behaviour as an option, for those who know what
they are doing when they turn it on.  However, this won't help you,
since it's a server problem, not a client problem.)

If your FreeBSD system is 2.2 or higher, you might give NFSv3 a try.

> Also, another Linux machine which reads from the DEC file
> system is reading old copies, possibly from its local cache.

That's either a bug in Linux's implementation, or (less likely) of the
server machine.

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)