Too much disk activity with OS 10.6 kernel and QNAP NAS TS-219+

When I boot up my iMac (OS X 10.6) everything works fine, can read/write files on the raid 1 array in the QNAP NAS box. The problem

is when I am not deliberately accessing files on the NAS. Every 1.5 to 2 seconds I can see led indication of disk activity and can hear it too.

When I sleep or shutdown this iMac, the disk activity stops, even though two other (OS X 10.5) machines remain on the network.

Used little snitch to identify network traffic. Seems the 10.6 OS kernel is communicating with the NAS, or vise versa every second or two.

This NAS is a replacement for an older D-Link unit I had which never exhibited this issue. Is there a setting I can change on the

OS X 10.6 machine (or NAS) to stop this constant accessing of the disk array?