Ah, Ben understands and did a great demonstration of thin provisioning (also read Dave’s Blog) with ZFS using sparse volumes (zvols).
HUGE.
The ability to thin provision storage is a very “enterprise” feature that one can know get from free when using ZFS+Opensolaris.
When combined with ethernet-based storage networks (iSCSI), it’s unstoppable.
Ben’s also a Joyeur now.
Welcome to the Family, Ben.
Jason A. Hoffman 
3 responses to “Thin Provisioning in ZFS”
I can understand overcommitting storage in a filesystem; writes will just return -ENOSPC when the fs is full. But when the pool backing your sparse zvol fills up, what happens?
Great to hear that Ben is joining you folks, Jason. It will be great to see what such creative and passionate people will bring to the table.
Thanks David!