NFS and kernel cache
- From: Chris Adams <cmadams@xxxxxxxxxx>
- Date: Wed, 20 Dec 2006 16:21:17 -0600
I'm copying a big chunk of data to a single file on an NFS server (in
this case, using ntfsclone to back up a NTFS partition). Both the
client and the server are on gigabit ethernet, and both are running FC6.
I see the disk LED come on solid for several seconds, then start
flickering, then go out for a second or two. If I watch the network
switch, it does the opposite: no traffic, then a burst of traffic.
Because of this, my total throughput is only about 200Mb/s.
My guess would be that the NFS client is letting a bunch of data queue
up, and that it doesn't start sending it until the disk has almost
filled the kernel buffers, so then the reads from the local disk stop
until the NFS client has written enough data to the server.
I also tried doing (the tr is in there to prevent a sparse file):
$ dd if=/dev/zero bs=1024k count=5000 | tr '\0' '\1' > /mnt/test/testfile
I can see the network start and stop on this. I do get about 320Mb/s,
but that's still a long way from what it should be.
Is there anything I can adjust to smooth out the network flow (and keep
this running to fill the network as much as possible)?
--
Chris Adams <cmadams@xxxxxxxxxx>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.
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