Hi guys,

Yes, the specialized metadata tier does improve dedup performance, however, 
this a general facility with many performance related aspects; there's much 
more can be done to address dedup performance specifically, some interesting 
ideas gave been discussed at prior open-zfs meetings, as I recall.

Boris 

Typos courtesy of my iPhone

> On Jun 26, 2014, at 9:49 AM, "Sarah Jelinek" <[email protected]> 
> wrote:
> 
> As Dan notes we have a special vdev class which you can use for a dedicated 
> dedup metadata or general metadata, or zil. This work was done by Boris 
> Protopopov. It generally improves dedup performance however, we still see 
> about a 4x degradation in performance(dedup vs non-dedup) even with the use 
> of the 'special' device. 
> 
> Certainly give it a whirl. We are currently working on getting this up to 
> date for integration into illumos so there will be some changes. We will post 
> performance data prior to the integration.
> 
> Regards,
> sarah
> 
> 
>> On Wed, Jun 25, 2014 at 8:17 AM, Dan McDonald <[email protected]> wrote:
>> 
>> On Jun 25, 2014, at 9:18 AM, Will Andrews <[email protected]> wrote:
>> 
>> > Hi,
>> >
>> > Has anyone worked on improving this feature lately?
>> 
>> Nexenta has done some work here. But I'm not sure how much of it is in the 
>> wild yet vs. still under development.  You should look at their illumos-gate 
>> child:  http://github.com/Nexenta/illumos-nexenta/ to be sure.  In 
>> particular, their "special vdev" class work (...zfs/special.c), where you 
>> can put metadata on a dedicated vdev.
>> 
>> Dan
>> 
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