Hi Eric,

A few things:

- Client-side provides better overall throughput for Spectrum Protect 
because the deduplication is spread across more CPU's. So if you can 
afford to do the deduplication client-side, that is the best overall 
result.

- Client-side helps reduce network traffic

- The algorithms on how deduplication is performed are the same between 
client and server.


The behavior you are seeing has to do with the reusedelay impact on 
deduplicated chunks. If the reusedelay is 1 day (default), that means 
Spectrum Protect keeps the deduplicated chunks pinned in storage until 
that time has passed. If the reusedelay is 0, there is a still a small 
cushion window that might allow the chunks to still be linked to. If you 
waited for a couple of hours AFTER the deletion occurred, I would not 
expect those chunks to be reused. 



Del

----------------------------------------------------

"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> wrote on 04/10/2017 
10:57:27 AM:

> From: "Loon, Eric van (ITOPT3) - KLM" <Eric-van.Loon AT KLM DOT COM>
> To: ADSM-L AT VM.MARIST DOT EDU
> Date: 04/10/2017 11:01 AM
> Subject: Deduplication
> Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
> 
> Hi guys!
> We are trying to make a fair comparison between server-  and client-
> side deduplication. I'm running into an 'issue' where I notice that 
> once you created a backup of a certain set of data, it is always 
> deduplicated 100% afterwards when you start a new client-side 
> deduped backup. Even when you delete all previous backup on the server 
first!
> So I backed up a directory, retrieved all objectids through a select
> * from backups and deleted all objects, but still a new backup is 
> deduplicated 100%. I don't understand why. I though it maybe had 
> something to do with data still being in the container pool, but 
> even with reusdelay=0, everything is deduplicated...
> Thanks for any help (Andy? :)) in advance.
> Kind regards,
> Eric van Loon
> Air France/KLM Storage Engineering
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