How many hard drives will you be running?
I'm not the ZFS expert, especially 32 bit as it's tricky and you are likely going to tweak some settings. There are some postings on these forums about tweaking 32 bit version of FreeNAS.
If you go with a mirror pair (2 drives) I think you will be fine but that's strictly a half-ass educated guess on my part. I feel if you are going to use 4 drives, you might be pushing it. Three drives is the minimum RAIDZ and you might get that. Post how many hard drives you desire to run and what kind of protection against hard drive failure you desire. As for prefetch, even mine is disabled at 4GB which does reduce read throughput for large blocks of data but I'm fine with what I have and I don't want that to introduce a problem into my system as well. Once we get closer to a final release product I might tweak the values.
Just to let you know, I have run a RAIDZ, Z1, Z2, mirrored pairs, and each drive as single ZFS drives on my system with 4GB RAM and have never touched the swap space. The maximum RAM I used was just over 3.2 GB so you might use the swap file if you plan to run 4 drives but with your controller card I have no idea if it will free up anything.
I'm sure someone will chime in that has experience with 32 bit FreeNAS and give you some friendly advice as well.
