You shouldn't ever use hardware RAID cards with ZFS because the processor in the RAID card is much slower than the CPU or the bus on the motherboard (your processor might be 2 gigahertz, but your hardware RAID card only runs at 500 megahertz), and using a RAID card with ZFS will just introduce high latency and slow everything down to a crawl. Also, when the RAID card goes bad (as mine once did) it will spew all kinds of random errors all over your hard disk drives and it will corrupt all of your data.
The point of using ZFS is that your data is incorruptible because the data is checksummed before and after it is written to disk and the file system is always consistent because data is never overwritten in place, but it is only incorruptible if you use the ZFS software RAID to mirror the drives instead of a hardware RAID card. As soon as you introduce a hardware RAID card, you are adding an extra layer of flawed technology that ZFS doesn't have control over and this creates the potential for errors and consequentially allows your data to get corrupted (which is what ZFS is supposed to prevent in the first place). The whole point of using ZFS is that it eliminates the need for hardware RAID cards by giving you the same kind of incorruptible file system that large enterprises (i.e. like banks and oil companies and large manufacturers) get by paying thousands of dollars for something like Netapp's WAFL file system. Except ZFS is free and WAFL isn't. -- This message posted from opensolaris.org
