The zpool is the uppermost ZFS structure.

• A zpool contains one or more vdevs, each of which in turn contains one or more devices.
• Zpools are self-contained units.
  • One physical computer may have two or more separate zpools on it, but each is entirely independent of any others.
• Zpools cannot share vdevs with one another.

ZFS redundancy is at the vdev level, not the zpool level.

• There is absolutely no redundancy at the zpool level.
• If any storage vdev or SPECIAL vdev is lost, the entire zpool is lost with it!

Modern zpools can survive the loss of a CACHE or LOG vdev.

• They may lose a small amount of dirty data, if they lose a LOG vdev during a power outage or system crash.

A zpool is not a funny-looking RAID0.

• It is a funny-looking JBOD, with a complex distribution mechanism subject to change.