On Sat, Nov 21, 2009 at 10:45 AM, Henrik Johansson <henr...@henkis.net> wrote:
> Hi all,
> If anyone is interested or have comments.
> I did a very quick test with zones on a deduped zpool and the footprint
> seems quite low, a little over 10MB per zone after the initial for OSOL
> default installed zone.
> http://sparcv9.blogspot.com/2009/11/dedupliation-with-zones.html
> (I know the spelling is wrong in the URL, not trivial to change without
> making a new post thought)
> Regards
> Henrik
> http://sparcv9.blogspot.com

The last time that I played with zones on OpenSolaris, the set of
software installed was small enough to not be terribly useful.  I
expect that as the size of the zone grows to accommodate a useful set
of software, the dedup ratio will be even more favorable.

About a year ago I was looking into how much duplicate data there is
in Solaris 10 zones that had been live anywhere between a day and 18
months.  The majority were sparse root zones, with a 500 MB soft
partition allocated as the zone path.  Any whole root zones were
created in a similar manner with a zone path of 4 - 8 GB.  I assumed
that the deduplication would be done at a 4 KB block size (ASIS on
NetApp) and as such calculated the md5 hash of each 4 KB block then
analyzed from there.  I believe the sample size was around 120 zones.

What I found was that there was that deduplication would be likely to
reduce storage needs for zone roots by 75%.  In other words, "sort -u
md5list | wc -l" was 25% of "wc -l md5list".  This number would surely
go up if the zones were full root zones or if the file system would
rewrite empty blocks with a consistent pattern (e.g. write 0's over
empty blocks).

In my case the vast majority of application binaries and data were not
in the sample as they are stored in file systems other than the

Mike Gerdts
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