ZFS Advice

[Wes Morgan]

I'm looking for information and advice from those experienced in building 
storage arrays with good performance. Thus far, I've simply been using a 
motherboard with a lot of built-in SATA ports. I've concentrated on making 
most of the investment in high quality storage rather than controllers, 
cases etc. It's just a 4U chassis (I don't even have a rack for it, too 
much $$$) with 16 hot-swap bays, for use as a media server. However, I've 
reached the point where I have a 8-drive raidz2. Any additional storage 
would need to be another independent raidz2 set, and there are not a lot 
of inexpensive options for go to 16 ports. So this brings up a few 
questions:

- Has anyone looked at what kind of workloads tend to perform best with 
prefetch enabled or disabled?

- Would I have better performance from a dedicated controller, and would 
the improvement be worth the cost? As it stands now, heavy read/write 
activity definitely interferes with both streaming and rtorrent.

- The 16-port controllers tend to have a lot of fancy "Intel RAID chips" 
etc, which is simply a waste of money when using zfs, right?

- Is one 16-port controller better than 2 8-port? Assuming two 8-device 
arrays, which will perform better?

- Which brand of controllers are best supported by FreeBSD? I've seen 
3Ware, Areca and LSI mentioned, and the prices are all pretty much the 
same. Can anyone share some of their experiences with these vendors?


Thanks,


WM