On 01/27/10 21:17, Daniel Carosone wrote:
This is as expected. Not expected is that:
usedbyrefreservation = refreservation
I would expect this to be 0, since all the reserved space has been
allocated.
This would be the case if the volume had no snapshots.
As a result, used is over twice the size of the volume (+
a few small snapshots as well).
I'm seeing essentially the same thing with a recently-created zvol
with snapshots that I export via iscsi for time machine backups on a
mac.
% zfs list -r -o
name,refer,used,usedbyrefreservation,refreservation,volsize z/tm/mcgarrett
NAME REFER USED USEDREFRESERV REFRESERV VOLSIZE
z/tm/mcgarrett 26.7G 88.2G 60G 60G 60G
The actual volume footprint is a bit less than half of the volume
size, but the refreservation ensures that there is enough free space
in the pool to allow me to overwrite every block of the zvol with
uncompressable data without any writes failing due to the pool being
out of space.
If you were to disable time-based snapshots and then overwrite a measurable
fraction of the zvol you I'd expect "USEDBYREFRESERVATION" to shrink as
the reserved blocks were actually used.
If you want to allow for overcommit, you need to delete the refreservation.
- Bill
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