NFS 100:1 performance loss

Schilling, Richard RSchilling at affiliatedhealth.org
Mon Aug 21 09:41:20 PDT 2000


Slow NFS because of UDP jives with the spec behind UDP: the broadcasts are
not guaranteed to arrive in a particular order, and are not guaranteed to
arrive at all.  

TCP is definitely the way to go for fast and reliable.  That's what FTP
uses.

Richard Schilling
Web Integration Programmer
Affiliated Health Services
Mount Vernon, WA 


> -----Original Message-----
> From: Mel Jones [mailto:mello at msg.ucsf.edu]
> Sent: Friday, August 18, 2000 3:50 PM
> To: josip at icase.edu
> Cc: Beowulf mailing list
> Subject: Re: NFS 100:1 performance loss
> 
> 
> Josip Loncaric wrote:
> 
> > Has anyone seen this NFS performance problem?
> >
> > Our Beowulf has two servers w/RAID-0 arrays which deliver 45MB/s,
> > connected via Gigabit Ethernet.  The machines are dual 
> PIII/500 systems
> > with 512MB of RAM each.  We are running Red Hat 6.2 updated 
> to kernel
> > 2.2.16-3 and recently we updated to nfs-utils-0.1.9.1-1.  
> We are running
> > 16 kernel nfsd threads on each machine.  Here is how long 
> it takes to
> > copy a 28,955,860 byte file from machine 1 to machine 2:
> >
> > rcp:       1.04 seconds (27.8 MB/s, where 1MB=10^6B)
> > ftp:       1.12 seconds (25.8 MB/s)
> > NFS 1KB:  12.35 seconds ( 2.3 MB/s, using rsize=wsize=1024)
> > NFS 8KB: 129.42 seconds ( 0.2 MB/s, using rsize=wsize=8192)
> >
> > Clearly, there is something very wrong with NFS, 
> particularly with 8KB
> > rsize/wsize (which should have improved performance!).  Our system
> > manager tells me that reduced Linux NFS performance with 
> 8KB rsize/wsize
> > is a known problem, but even at 1KB our NFS is getting less 
> than 10% of
> > the rcp or ftp performance.
> >
> > Any ideas?
> > Josip
> >
> > --
> > Dr. Josip Loncaric, Senior Staff Scientist        
> mailto:josip at icase.edu
> > ICASE, Mail Stop 132C           PGP 
> key at http://www.icase.edu./~josip/
> > NASA Langley Research Center             
> mailto:j.loncaric at larc.nasa.gov
> > Hampton, VA 23681-2199, USA 
>    Tel. +1 757 864-2192  Fax +1 757 864-6134
> >
> > _______________________________________________
> > Beowulf mailing list
> > Beowulf at beowulf.org
> > http://www.beowulf.org/mailman/listinfo/beowulf
> 
> I've seen a similar but nowhere near as bad result on our 
> network. This may
> be completely irrelevant but I found NFS traffic between my 
> SGI machines
> about 4x slower than FTP. It got much better when I set the 
> transport to
> TCP rather than UDP.  The problem turned out to be that my 
> switches weren't
> necessarily forwarding the packets in order of receipt and 
> this was taken
> care of much more efficiently on the receiving machine with TCP.
> 
>             ... mello
> 
> 
> 
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> 
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