Underprovisioning a ZIL necessary?

[leonroy]

I've noticed that when using the ZFS Storage Wizard, FreeNAS still partitions a ZIL as a single partition using all the space on the disk.

Since most modern SSDs include wear levelling in the drive itself is underprovisioning a ZIL (to 2x transaction group) still necessary?

 

[HoneyBadger]

I believe most drives will do wear-leveling over free space within a partition, but it will only "clean up after itself" if there's enough idle time to issue TRIM commands. An SLOG doesn't necessarily get that idle time, so it's good best practice to underprovision.

In order of best to worst:

- Set up Host Protected Address in the drive itself
- Use a BIOS-specific size limit
- Manually create a smaller ZFS partition on the drive from the command-line
- Assign the whole drive

Whichever one you do, you should use either the ATA SECURE ERASE command or your drive vendor's tools to erase all cells first, and then set it up.