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

[grarpamp]

> ZIL is there for you to recover transactions in case of a crash.
> It is your safety net.

I always thought the ZIL was pushed out safely. So that still
no matter what the disk would be consist [1]. Like when crash
you just lose the ZIL's since the last ZIL push. Which odds
are will be just work product here.

> Use the RAM for ARC, it will provide more performance.

But about reducing fragmentation without separate ZIL.
I'm admittedly over full and will need to move data to
new pool anyway. Just that with ZIL in main pool what article
I read says problem can mostly come back without separate zil.
I tend to run full till annoyed to redesign, bad habit.

> If you don't have low latency SSD, put it on separate spinning disk

This may be best. But ties to [1] above.. if ZIL spindle (even mirrored)
dies, what is the point of what ZIL is on if ZIL separate from main
pool is unsafe anyways.

> USB ... unreliable

I would have to test USB bus and devs for stablility. But
I do have local lifetime warranty on 32GiB devices :)
So maybe mirror 2 of them, or 2x2.
Due to crypto I only get 7-15MiB/s on spindle anyway.

> Why don't just set sync=disabled?

Hmm, that might give performance as on any FS, but unsure about lesser
fragmentation. I should find something to read on that.

> What is split ZIL?

Separate from main pool (spindles), 'zpool ... log ...'

This may become an experiment :)