Windows server 2016 Deduplication and robocopy

Hi experts,

I think this is quite a simple question.
Following scenrio:

I set up a new Windows Server 2016
I initially robocopied (/E /V /L /COPY:DAT /TEE /R:1 /log:) a file share from my old fileserver (without dedup) to a new one when dedup was not yet activated on the target.
After that I activated dedup (59% rate) and I have an optimzed state of the share on my new server.
I would now like to sync the old share (which is still in production) with the new one.

At the moment I am trying the same robocopy command again (as dryrun) and in the robocopy logfile I see entries with "equal" and some with "optimized".

Would the sync work in that scenario? (Target optimized, source unoptimized)
I`m definitely only copying a folder, not the whole volume what did make problems with dedup for others, how I read.

Many thanks in advance!
Who is Participating?
Jeremy WeisingerConnect With a Mentor Senior Network Consultant / EngineerCommented:
What exactly would that mean?
Are you referring to the block level vs file level? If so, block level means that a whole file doesn't need to be duplicated to see a savings. By doing it at the block level it means that any blocks on the disk that are identical can be deduped regardless of the file its associated with. The advantage is that the file format and data types are irrelevant and so matching blocks can be found among disparate data.

Can I use robocopy after activating deduplication and then sync the directories? Or would I have to wait for dedup activation until I have all date copied to the target?
You can turn on dedupe right away. Robocopy and deduplication are completely separate and don't have any bearing on each other.
Jeremy WeisingerSenior Network Consultant / EngineerCommented:
Dedupe is local to the volume. The source of the files makes no difference where you copy them from. The dedupe process runs periodically on the server (depending on the settings) and will optimize the files over time. I think the default setting is to optimize files 5 days old and older on the volume.
SystemadministrationAuthor Commented:
Yes correct.
The policy is "files older 3 days"
My question is, whether robocopy is able to recognize if I file in the target is equal/different from the source, even while deduplication is activated on the target.
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
No, robocopy won't do that. The groveler service needs to make that determination and process all files.

Note also that the dedupe in Windows is not file based but block based so it can dedupe portions of files that are the same.
SystemadministrationAuthor Commented:
What exactly would that mean?
Can I use robocopy after activating deduplication and then sync the directories? Or would I have to wait for dedup activation until I have all date copied to the target?
PberSolutions ArchitectCommented:
No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

Accept: Jeremy Weisinger (https:#a42366290)

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