ZFS - Pools - Add Intent Logs to a Pool

ZIL (ZFS Intent Log) drives can be added to a ZFS pool to speed up the write capabilities of any level of ZFS RAID.

One normally would use a fast SSD for the ZIL.
Conceptually, ZIL is a logging mechanism where data and metadata to be the written is stored, then later flushed as a transactional write.
In reality, the ZIL is more complex than this.
One or more drives can be used for the ZIL.

Add a drive to the pool for ZIL

sudo zpool add testpool log /dev/sdg -f

NOTE: This can speed up writes.