I have a device that sends out information at 4.7 Megabytes a second.
I have a desktop that receives the data from this device that runs Red
Hat Enterprise Linux 5.5. They are on the same switch, a 24-port
Juniper EX2200.
When I write the data to the desktop on the local filesystem, there's
no dropped information. When I write the data to an NFS share, the
device reports dropped packets.
I have tried playing with the rsize/wsize NFS parameters (8192K seems
to be the best value), and values in
/proc/sys/net/core/{r,w}mem_{default,max} and increasing the NFS
daemon count, as suggested by
http://nfs.sourceforge.net/nfs-howto/ar01s05.html. Very similar
results across the board.
The NFS server also runs RHEL5.5. It's got 11 600gb 15k SAS drives in
a hardware RAID6 array. Running 'iftop' on the machine during the data
gathering operations, I'll see bursty traffic... that is to say,
workstation -> NFS server traffic will be in the high 40mb/sec rate,
then slow down, and once it slows down the device I refer to complains
of dropped information then it'll speed up again.
I find it hard to believe that a machine on the same (recent, gigabit)
switch can't write out 4.7MB/sec. Am I wrong?
Does anyone have any NFS or TCP tuning recommendations that may be a
little more up to date than the NFS howto that was last updated in
2006? I'm really at a loss here.
Thank you, more than a lot, in advance..
- Pat
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