Its difficult. If one disk fails you lose everything on it and
Elasticsearch gets upset until you shut down the service and remove the
disk from its path.data and start it again. This is the best case scenario.
As it is now I suspect it'll amount to the same thing as losing the whole
RAID0 - the files on the other disk aren't super useful if you have
replicas because they won't contain a full replica (until that commit you
mention) and elasticsearch will have spun up a new replica when it noticed
that that node was down anyway. It might have trouble noticing too.
If you have 2 disks in the system I'd go RAID0. If you have ten then RAID10
- though that is just my gut from relational db days. They hate RAID5/6. I
suspect ES actually is less bad but I don't know how much.