feature request: persistent l2arc

[kez-kuehl]

Hello,

I know persistent l2arc has been dropped from the agenda, but I think it's important for desktop adoption. It would reduce the dependecies.

Config Today:
SSD Cache: LVM / bcache
Crypt: LUKS
[...]

To:
ZFS

[lundman]

I was working with someone on IRC about that (unfortunately appears to be MIA though?) where we found the latest commit (probably) and re-merged it into a fresh tree:

https://github.com/openzfsonosx/zfs/tree/persist_l2arc

Alas, there are some questions regarding how it should interact with ADB calls;

openzfsonosx/zfs@3ccc612#diff-163982413ed6b6861e08633c89a77395R9948

But if that can be figured out, it could be tested and all that.

[gertvdijk]

See #3744

[PrivatePuffin]

@behlendorf
I think you want to get rid of this one in favor of #3744

#3744 has a good description and links to all other discussions. This Issue is just bloat.

[behlendorf]

Duplicate of #3744.