On Mon, 05 Nov 2018 11:07:12 -0500, "Austin S. Hemmelgarn" said:

> Performance isn't _too_ bad for the BTRFS case though (I've actually
> tested this before), just make sure you disable direct I/O mode on the
> loop device, otherwise you run the risk of data corruption.

Did you test that for random-access. or just sequential read/write?
(Also, see the note in my other mail regarding doing a random-access
write to the middle of the file...)