On Fri, Oct 17, 2003 at 06:43:40PM -0400, Jon LaBadie wrote:
> I tried some throughput checks today. Test one was a "cp -r"
> of a directory tree with 8.5GB (only a few large files) and
> test two was a ufsdump of a 1GB partition. Both gave between
> 3 and 3.5MB/sec rates to the NFS device. That certainly is
> higher than the 1MB/sec I get to tape, but quite a bit lower
> than the rate to a local disk.
NFS-2 write performance is lousy, since the server needs to
effectively fsync() on every write() call before it returns
status to the client. (I suspect that one tends to notice this
with large files more than with small ones, because we expect
lots-of-small-file performance to be worse in any case.)
NFS-3 is supposed to be better, as is FreeBSD's "nqnfs" (the "nq"
stands for "not quite"), but I've never tried either.
Here's a test, in addition to the ones Tony suggested:
- Try copying a single large file from local disk to the
NFS-mounted drive
- Try copying the same large file, to the same partition on the
NFS server, using FTP (if you use scp instead, turn off
compression to keep it from becoming CPU-bound and confusing
things)
Comparing the length of time for those two tests will tell you
how much of the problem is in NFS itself, and how much is in the
lower layers of the networking subsystem.
Also, if you can sit beside the Snap Server when doing those
tests, listen to it. If its disks make noise when they seek, I
bet you'll hear a *lot* more of that during the NFS test than
during the FTP one. If there's a disk-activity LED, you might
see a difference there too. (I don't know how this manifests in
more scientific measurements like iostat results, if it does at
all... The completely unscientific seek-rattle is more
viscerally convincing anyway; at least I found it so :-)
--
| | /\
|-_|/ > Eric Siegerman, Toronto, Ont. erics AT telepres DOT com
| | /
When I came back around from the dark side, there in front of me would
be the landing area where the crew was, and the Earth, all in the view
of my window. I couldn't help but think that there in front of me was
all of humanity, except me.
- Michael Collins, Apollo 11 Command Module Pilot
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