[bscphil]

Out of curiosity, how much total storage do you get with that drive configuration? I've never tried "bundle of disks" mode with any file system because it's difficult to reason about how much disk space you end up with and what guarantees you have (although raid 1 should be straightforward, I suppose).

[tuetuopay]

I get half of the raw capacity, so 7.5TB. Well a bit less due to metadata, 7.3TB as reported by df (6.9TiB).

For btrfs specifically there is an online calculator [1] that shows you the effective capacity for any arbitrary configuration. I use it whenever I add a drive to check whether it’s actually useful.

1: https://carfax.org.uk/btrfs-usage/?c=2&slo=1&shi=1&p=0&dg=1&...