After changing servers and moving things around, I have one system which serves the /home directories, and for some reason, it is extremely slow. I've looked for duplicate IPs, signs of a HW problem, etc. and cannot figure out why the system is running with a high load, high iowaits, and low responsiveness.

The servers and clients are slackware 12.2 and 13.1 respectively.

So I did some more digging. I ran tcpdump with a variety of filters (essentially using grep), trying to find out what might be happening.

I found that the problem is unique to my server, as clients can nfs betweeen each other with good transfer rates, bidirectionally, at good rates (10 MB/sec) using large files for testing (time dd). Any of my clients has a problem with the server, and none of them have a problem with each other.

Most recently, I found when the errors are occuring, there is a Unknown rpc response code, which appears to be regularly changing.

Pointers anyone?

I think there may be something wrong with portmapper .
rsize and wsize parameter can also improve performance.

Thanks

Well, I found two things.

I tried swapping the interfaces around in the oldbox, and that did not work. Then I found that there was a router on the network, which answered to the same IP as the oldbox, in addition to it's assigned IP.

Neither of those fixed things. Then I decided to do something I hadn't done in the last couple of days that I was working this problem. I powered down oldbox.

When I booted it up, everything started working as it should.

Go figure.