On Feb 9, 2010, at 7:24 AM, Kjetil Torgrim Homme wrote:
> Richard Elling <richard.ell...@gmail.com> writes:
>
>> On Feb 8, 2010, at 6:04 PM, Kjetil Torgrim Homme wrote:
>>> the size of [a DDT] entry is much larger:
>>>
>>> | From: Mertol Ozyoney <mertol.ozyo...@sun.com>
>>> |
>>> | Approximately it's 150 bytes per individual block.
>>
>> "zdb -D poolname" will provide details on the DDT size. FWIW, I have a
>> pool with 52M DDT entries and the DDT is around 26GB.
>
> wow, that's much larger than Mertol's estimate: 500 bytes per block.
argv! I miscalculated, the size is approximately 14.2GB, not 26GB.
That leads to approximately 270 bytes per record.
>
>> $ pfexec zdb -D tank
>> DDT-sha256-zap-duplicate: 19725 entries, size 270 on disk, 153 in core
>> DDT-sha256-zap-unique: 52284055 entries, size 284 on disk, 159 in core
>>
>> dedup = 1.00, compress = 1.00, copies = 1.00, dedup * compress / copies =
>> 1.00
>
> how do you calculate the 26 GB size from this?
The exact size is not accounted. I'm inferring the size by looking at the
difference
between the space used for the (simple) pool and the sum of the file systems
under
the pool, where the top-level file system (/tank) is empty with mount points,
but no
snapshots.
$ zpool list tank
NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT
tank 100G 43.9G 56.1G 43% 1.00x ONLINE -
$ zfs list -r tank
NAME USED AVAIL REFER MOUNTPOINT
tank 44.0G 54.5G 25K /tank
tank/d 18.4G 54.5G 18.4G /tank/d
tank/d2 11.3G 54.5G 11.3G /tank/d2
tank/test 22K 54.5G 22K /tank/test
-- richard
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