ZFS Striping and Optimizing Capabilities

[Chris Telting]

Just a few questions about what ZFS actually does.  So if anyone has 
intimate knowledge about ZFS's implementation on Freebsd I'm sure I and 
others would appreciate the answers.

When you add a second and or thrid drive/partition to a zpool I'm 
assuming that it's going to start using the drives like a raid 0 
stripe.  How do the ZFS versions differ in this?  Does it immediately 
start striping all files in the background on low priority or does it do 
it as files are accessed?  Does ZFS in any way do performance testing of 
read/right operating in light of where the data is stored on the drive? 
i.e. the outside sectors of hard drives perform faster.  If it does do 
read/write location testing can it be shut off or does it detect SSDs?  
What about tracing application sector reading and reordering sectors so 
that they follow one another according to typical usage?  i.e. the 
sectors are already in the linear read ahead buffer?

I appreciate any answers,
Chris