high load copying between filesystems
 

We recently installed 2 dual-port qlogic 4Gb HBA's in a dell 2950 running RHEL4u6 32bit with 4x2.66GHz cores along with 16GB. These are connected to an IBM SAN and running RDAC for multipathing.

The admin who manages the processes on this machine noticed that while doing a straight copy of data from one filesystem on the SAN to another on the SAN, that the load would spike. I'm not sure if this is expected behavior or not, but it is concerning, and I'm at a point where my experience is quite limited.

In this case we are attempting to cp a 14GB file, and I'm seeing the load average going up to 9.

Any thoughts as to why this is?

I have also seen this behavior on a couple of my systems. Also interested in what causes this.

I would suggest that this is caused by processes waiting for I/O ("D" state in top).