Finding the bottleneck in Nexenta?

I built a Nexentastor server (free edition) and I am having serious disk performance issues.

This same box had FreeNAS on it before and it was much much faster.

Here are the specs: Dual core E6600 cpu 4GB of good memory 6x 1.5TB Seagate drives plugged into the ICH10 controller (no raid) ZFS (version 24 I believe)

I installed pure-sfv and unrar.

a pure-sfv check on a ~1GB folder takes a few seconds, this is nice and fast, no problems.

But the unrar on the same files takes forever (~7-8 minutes)

I took the same folder and moved it to a linux laptop (dual core, 4GB of ram cheap 160GB disk) and the unrar only takes 30 seconds.

Any ideas what can be causing this?

When I view the load while extracting the disks are going 200-6000KB/s read and about 2000KB/s write, the cpu is at about 10% (8-10%)

This just does not seem right to me.

Could it be unrar being silly? compile issue perhaps?

Thanks.

Luc