Software RAID performance? RAID-Z or vinum and RAID5?

[Mike Manlief]

I'm looking into moving a workstation from Ubuntu 10 to FreeBSD 7.1
(both amd64) and I'm a bit worried about storage -- specifically
moving from mdadm, which performs very well for me.

Current in Linux I use an mdadm RAID5 of 5 disks.  After investigating
FreeBSD storage options, RAID-Z sounds optimal[1].  I'd like to avoid
levels 3 and 1 due to write bottlenecks[2], and level 0 for obvious
reasons.  Migrating from the existing mdadm is not an issue.  I also
do not plan to boot from the software array.

Various docs/postings seem to indicate that using ZFS/RAID-Z under
FreeBSD will destroy my computer, run over my cat, and bail out the
investment banking industry.  Will it really perform that poorly on a
Phenom and 8GB RAM?  Significantly more resources than mdadm in Linux?
 How about compared to RAID 5 under vinum?

Thanks,
~Mike Manlief

1: The ability to read the array with the Linux FUSE ZFS
implementation is very appealing; don't care about performance for
such inter-op scenarios.  Copy-on-write sounds awesome too.

2: ...and even level 5, now that I've learned of RAID-Z.