Re: btrfs balance enospc

[Mark Murawski <markm-lists@intellasoft.net>]

 > Does/should a balance imply removal of missing devices (as long as 
the minimum number of devices are still available)?

That's a really good question.  As a user I would expect it to balance 
over remaining devices assuming you still have a complete picture. 
Doing a device delete missing after a balance should be just some pool 
metadata updates at that point.

Anyway... I solved my problem by moving/deleting files to free up space 
to the point that balance no longer complained about enospc.

I suppose btrfs needs extra working space to do a balance... above and 
beyond the actual size of the existing data/metadata to be moved?  I had 
a total of three devices, with what appeared to be plenty of space on 
the two that were to be remaining, but balance/remove was still 
complaining to be out of disk space.

It would be a good idea for some metrics to be calculated upon start of 
a removal or balance to tell the user "hey you need to free up XXX more 
bytes in order for this operation to be successful".