On 2012-10-25 22:11, cwillu wrote:

quoted

quoted

3. How does Data: total=72GB before rebalance, but is 5GB after
rebalance? This was a brand new file system, file system
installed, with maybe 2-3 updates, and a dozen or two reboots.
That's it. No VM's created on that volume (it's a VDI itself),
and the VDI file itself never grew beyond 9GB.

Combine the previous two answers: You had 72GB allocated to block 
groups which are mostly empty.  After the balance, the contents of 
those groups have been shuffled around such that most of them could
be freed.

Did btrfs rebalance when it needs spaces ? The example reported by Chris
suggested that due to the filesystem history, btrfs allocate some chunk
that became empty.
If the user/admin don't make a (re)balance, is btrfs capable to move
some chunk from the DATA pool to the METADATA pool when the space became
low autonomously ?
I don't think, but I want a confirmation.

BR
G.Baroncelli

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