Hi,

On 2016-08-26 13:52, Austin S. Hemmelgarn wrote:

Regular 'df' isn't to be trusted when dealing with BTRFS, the only
reason we report anything there is because many things break horribly
if we don't.

Yeah, I noticed. Seems to produce a reasonable guess, though.

Additionally, while running with multiple profiles while not balancing
should work, it's pretty much untested, and any number of things may
break.

Oh. Good to know.

Assuming your two disks have similar latency and transfer
speed, you're almost certainly better off just converting completely
to single mode (which works like raid0, just at the chunk level
instead of the block level).

Okay, I see.

On a slightly separate note, if your doing backups more frequently
than once a week, your probably better off just leaving the disks
connected and running.  Regular load/unload cycles are generally
harder on the mechanical components in modern disks than just leaving
them running 24/7.

True. A bit of context: I first want to make a full backup locally, then 
use the disks off-site for nightly incremental backups via internet.

Cheers
Gert