Crazy ZFS ZIL options: md(4) umass(4)

[grarpamp]

I have thousands of small files being written most under 8KiB, they
either end up being removed or combined in various ways to
produce a set of data that is stored long term. I also have
tens of 10-50MiB files similarly, but rarely. It's not fully clear
to me the benefits of a split ZIL. Some say a split ZIL will ward
off some fragmentation, which pushing over 80% I'm sure to see
otherwise. Plus a speed boost if on faster media. And maybe
even no need to commit some ZIL to disk as small files are
removed before ZFS decides to aggregate?

Anyway, use case aside, I can put 1GiB of ram as ZIL.Same for 32GiB USB.
RAM is obviously fast and power fail prone.
USB is slow and power safe.
Either could be mirrored, 2xRAM, 2xUSB.

- If I lose power on RAM, will the disk still be consistent?
- What data integrity does ZIL have? None? ZFS dataset's sha256?
- Any production experiences with this crazy ideas?

Thx.