Hi Stuart,
The reason why "used" is larger than the volsize is because we
aren't accounting for metadata, which is covered by this CR:
http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6429996
6429996 zvols don't reserve enough space for requisite meta data
Metadata is usually only a small percentage.
Sparse-ness is not a factor here. Sparse just means we ignore the
reservation so you can create a zvol bigger than what we'd normally
allow.
Cindy
On 10/17/09 13:47, Stuart Anderson wrote:
What does it mean for the reported value of a zvol volsize to be
less than the product of used and compressratio?
For example,
# zfs get -p all home1/home1mm01
NAME PROPERTY VALUE SOURCE
home1/home1mm01 type volume -
home1/home1mm01 creation 1254440045 -
home1/home1mm01 used 14902492672 -
home1/home1mm01 available 16240062464 -
home1/home1mm01 referenced 14902492672 -
home1/home1mm01 compressratio 11.20x -
home1/home1mm01 reservation 0 default
home1/home1mm01 volsize 161061273600 -
home1/home1mm01 volblocksize 16384 -
home1/home1mm01 checksum on default
home1/home1mm01 compression gzip-1 inherited from
home1
home1/home1mm01 readonly off default
home1/home1mm01 shareiscsi off default
home1/home1mm01 copies 1 default
home1/home1mm01 refreservation 0 default
Yet used (14902492672) * compresratio (11.20) = 166907917926
which is 3.6% larger than volsize.
Is this a bug or a feature for sparse volumes? If a feature, how
much larger than volsize/compressratio can the actual used
storage space grow? e.g., fixed amount overhead and/or
fixed percentage?
Thanks.
--
Stuart Anderson ander...@ligo.caltech.edu
http://www.ligo.caltech.edu/~anderson
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