A couple ZFS questions

[Quartz]

Inside a thread on -questions, it was asked if was a bad idea to have a 
ZFS array that spanned different controllers (ie; motherboard sata + 
pci-e sata). I answered that AFAIK it was ok as long as the speed of the 
onboard ports+drives and card+drives aren't drastically different and 
that the drives are the same. But it occurred to me that maybe that's 
not true [anymore]. Can anyone with more hardware knowledge chime in?


Also: What's the best practice advice these days for how resilvering 
should be set, assuming that "rebuilding the array before another drive 
dies" is the only goal? Should the resilver be maxed out so it completes 
as fast as possible before another drive dies, should it be set as low 
as possible to minimize load on the other drives to reduce the chances 
of one dying, or does it matter?