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Data Corruption, only in Pool drive?



Ok, so I've got 5x3Tb pool with 2x duplication on about half the folders, probably 10tb total space used.


I'm having trouble where I can read a file fine from any of the original drive hidden pool folder, but the data appears corrupted when I try and use the file from the pool drive.  Videos are unreadable, ISOs unmountable, etc,etc


Any ideas?  


I'm also running data deduplication on server 2012r2 (only on source drives, not pool drive), but i thought since drivepool operated only at the file level, that would be ok.



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To be clear, you're using Data Deduplication on the disks that are IN the pool, correct?


If so, then there is an advanced setting that you HAVE to enable to (hopefully) get this to work, otherwise, you will definitely see the issues that you are reporting.



Find "CoveFs_BypassNtfsFilters" and set this to "False".


However, even with this setting configured, it may not work. 




The reason for this is how the Deduplication process works.

Specifically, it uses a file system filter (you can view these with "fltmc"). 

Normally, when you access the file, the filter intercepts the request and can modify it (this is also how antivirus programs work). 

Deduplication requires this, as only part of the file is stored in the normal location. The deduplicated part is stored elsewhere on the disk (in the "System Volume Information" folder, actually, I think). 


So when you access the file normally, the DeDup filter re-joins the deduped data with the rest of the file, to present the whole file.



However, the driver for the pool bypasses the NTFS filters (for performance and compatibility reasons). This means that the Pool is only picking up the non-deduplicated data, and present "corrupted" files to you.

Disabling the "BypassNtfsFilters" option will cause the pool to respect the filters, and should "fix" the data.

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Ok, yes -- I remember you telling me I needed to do this on a previous topic.  I just now went in with a Admin notepad and changed that setting to false.  I've both restarted the drivepool service and rebooted the box, but it still "presents" the files on the drivepool drive as invalid, most of the time not even letting me do things like copy, etc.

Are there any other settings you can think of for me to change, or a way to know that my changes to the service config file took effect?

Also, is there any logging I can turn on that can shed light here?


If I can help get to the bottom of this, I'm glad to help!

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