storage - ZFS over iSCSI high-availability solution

I am considering a ZFS/iSCSI based architecture for a
HA/scale-out/shared-nothing database platform running on wimpy nodes of plain PC
hardware and running FreeBSD 9.

Will
it work? What are possible
drawbacks?

Architecture

1. Storage
   nodes have direct attached cheap SATA/SAS drives. Each disk is exported as a separate
   iSCSI LUN. Note that no RAID (neither HW nor SW), partitioning, volume management or
   anything like that is involved at this layer. Just 1 LUN per physical
   disk.




2. Database nodes run ZFS. A ZFS
   mirrored vdev is created from iSCSI LUNs from 3 different storage
   nodes. A ZFS pool is created on top of the vdev, and within that a filesystem which in
   turn backs a database.




3. When a disk or
   a storage node fails, the respective ZFS vdev will continue to operate in degraded mode
   (but still have 2 mirrored disks). A different (new) disk is assigned to the vdev to
   replace the failed disk or storage node. ZFS resilvering takes place. A failed storage
   node or disk is always completely recycled should it become available
   again.





4. When a database node
   fails, the LUNs previsouly used by that node are free. A new database node is booted,
   which recreates the ZFS vdev/pool from the LUNs the failed database node left over.
   There is no need for database level replication for high-availability
   reasons.

Possible
Issues

• How
  to detect the degradion of the vdev? Check every 5s? Any notification mechnism available
  with ZFS?




• Is it even possible to
  recreate a new pool from existing LUNs making up a vdev? Any
  traps?