What is the difference between these

[Bruno Scota]

Guy, I have a server with 12disks with 1T each and i need to make a iscsi store to backup my VM's. When go to volume manager i and try to configure a RAIDZ2 got this options(see images). So, which one is the best, or just what is the difference ?

 

[Dusan]

The first one is a stripe of two 6 drive RAIDZ2 vdevs.
The second one is a one big 10 drive RADIZ2 (and you still have 2 drives unassigned).
I recommend you read cyberjock's guide. It nicely explains everything: http://forums.freenas.org/threads/slideshow-explaining-vdev-zpool-zil-and-l2arc-for-noobs.7775/