ZFS raid write performance?

[Quartz]

>> I guess a better way to word the question is: would a raidzX using
>> generic drives, samba, and 500mb-4gb files be notably slower at writing
>> than ~70mb/sec. I have a feeling not, but I wanted to double check.
>
> Gut feeling: I'm sticking with the network being the limiting factor.
> But the only real way to know is to setup a test system and, well, test.

Question: I'm not super familiar with the way freebsd+zfs handles IO and 
caching under the hood, especially not when you throw drive caching into 
the mix too. Does something simple like "dd if=/dev/zero of=/pool/foo 
bs=1m count=500" give me a reasonably accurate number for write speed?