Slower write speed with ZFS RAID-Z compared to linux RAID5

[flawl3ss]

I recently redid my file server and removed Ubuntu with ext3 and software RAID5 with which I was able to get 85 MB/s writes over Samba and put FreeNAS 8.0.4-RELEASE-p1 64-bit. My write speeds over Samba with FreeNAS are now 23-30 MB/s using a RAID-Z configuration. Could this be a configuration on my end causing this or is it simply the ZFS implementation in FreeBSD that's the cause? What are some things I can do to narrow down what is causing the significant write speed difference?

Here are some hardware specs that may be relevant...

RAM: 4 GB DDR2
CPU: 3.0 GHz AMD X2 6000+
Hard drives: four Hitachi 1TB
Free space: 399 GB of 2.9 TB
NIC: Onboard nVidia - nfe0: <NVIDIA nForce MCP77 Networking Adapter>

[flawl3ss]

Turns out the problem is with the lack of support for the nForce/Realtek chipset which is causing the slow transfer speeds across the network. I put in a supported Intel NIC and my speeds are back to normal!