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Windows Server 2012r2 Deduplication


I was reading the changlog and I read;


* [issue #13517] When the "dedup" file system filter is installed, "Bypass file system filters" is overridden and
disabled. This allows pooled drives that are utilizing data deduplication to work correctly with
StableBit DrivePool.


Is this for the Windows Server 2012r2 Data Deduplication Service?


It's been a while and I've been using mhddfs and I was looking into swapping my server back to Windows for ADDC, and some other stuff that is easier to do in windows.


Right now I do a hardlink of my Finished folder to another folder called Sort. I then move all the Finished data to Deletable. I can then sort the files in Sort into other directories without issues caused by renaming. This lets me seed to 2.0 in peace without space waist. I was wondering how DP would handle this.


So how does DP handle hardlinks right now?


Before it gets asked, I'm using Snapraid instead of DP's duplication system. A 2-disk parity saves a lot of space. If I can hardlink and/or use Deduplication that would further save space.

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Yes, this is specifically for the Windows Server 2012R2 Data Deduplication feature. Since it's not installed by default, if we detect it, the setting is changed automatically (and can be toggled back on).


However, deduplication is PER DRIVE. It's not global for the pool.  So the savings isn't going to be as good.

But you can use the File Placement Rules to control what file types or folders end up on which disk, to maximize savings.



And no, DrivePool doesn't handle hard links on the pool. It handles just about every other form of file system link, though.




 Hard Links are not implemented using reparse points and so this build of StableBit DrivePool does not support them. Hard Links are implemented directly in NTFS and can only point to a file on the same volume.

Since the Pool is an emulated file system, we can't create NTFS objects like this. Additionally, since DrivePool accesses a bunch of different volumes.... 

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Is implementing Hard Links possible?  Can DrivePool detect that the user is creating a hard link?  If so, can DrivePool detect the real volumn(s) the source file is on?  If so, couldn't DrivePool keep the link on the same source volumn(s)?


Hard Links link files on the same volume.

They're also an NTFS object, and not implemented in the same way that reparse points are.  That means we'd have to store them on each individual disk in the pool, and figure out how to make them work.

Keeping them on the same disk works for unduplicated data. But what happens when you start duplicating data. And when you need to move or place some files on other disks? 



It may be possible, but the complexity to implement it ... well, reparse points were very complicated to implement. Hard Links may not be possible to do in a meaningful way.  And we'd rather spend the time figuring out how to support VSS and/or USN Journalling first, as these are much more useful and frequently used file system features.

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