I love the idea of using SSD EBS instance stores as L2ARC and ZIL for a zpool backed by EBS.
Going further (and into more dangerous territory), could I instead create a zpool mirror with the 2 instance stores:
zpool create vol1 mirror xvdb xvdc
and then use ZFS snapshotting/replication to keep a "warm"/eventually consistent spare on EBS?
- I would be OK with losing a few seconds of data
- I don't want to add the EBS as a hot spare, because that would limit the speed of the whole pool