Monday, October 8, 2012

Error 0x80070780 reading from a deduplicated drive

I read somewhere that Windows 2012 deduplication is not part of a new NTFS version, but it is instead a sort of a engine which is layered on the file system. To test this I decided to mount a NTFS-Windows-2012-deduplicated-external-USB-drive on a Windows 2008 R2 server (which since Windows XP has the same NTFS version, 3.1).
NTFS File System Driver version and size compared between Win2008 and Win2012
If the initial statement is right and the NTFS version is the same, I should be still able to read this external deduplicated drive with Windows 2008 R2. My test revealed this to be true. I can see the USB drive and browse its folders but, when I try to open any file bigger than 32 kbytes, I get the following error message:
Error 0x80070780 The file cannot be accessed from the system
Now if I check with Powershell the attributes of any of these files stored on the deduplicated drive and whose size is larger than 32KB, I get:
Get-Item 40kb.txt | select Attributes | fl
Attributes : Archive, SparseFile, ReparsePoint
On smaller files, only the 'archive' attribute is present:
Get-Item 20kb.txt | select Attributes | fl
Attributes : Archive
So, the attributes of a deduplicated file are: sparse and reparse point.

I thought it would be useful to share my experience on this in case somebody need it.


  1. Please email me. I have been searching for information that has caused one of my drives to receive this exact error on files over 32KB. The issues occurred sometime after refreshing my Windows 8 installation.I have about 500GB of important data that is inaccessible by my windows install. I have tried every permissions and attribute trick I could find including re installing windows on a clean format. The only thing is every reference to this error all seem to be about either windows server of WHS. The disk is dynamic and I am not sure how to resolve the NTFS version issue if that is indeed what it is. Please contact me if possible,

    1. Hi Dominic,

      did you manage to enable deduplication on that drive after reinstalling?
      Use these commands to enable dedupe:

      Import-Module ServerManager
      Add-WindowsFeature -name FS-Data-Deduplication
      Import-Module Deduplication
      Enable-DedupVolume F:

      Of course replace F: with your drive letter.

      Let me know whether it worked or not.

    2. @Carlo
      Exactly what I needed for my restored LUN to be able to access files again. Many thanks!

  2. Holy Crap! Thanks for the update, thought I lost my whole file share!

  3. Hi,
    I had the same Situation on Windows 2012 R2 after reinstalling fron Windows 2012. The previosly dedup-enabled volumes could not be read.
    After enablling dedup all went well again

  4. There was a file hack that allowed deduplication on Windows 8 and I forgot I had it running on a large NAS over 3TB. I reinstalled Windows 8.1 and the hack didn't work again, and I thought I lost all the data files on the NAS. Lucky for me Server 2012 R2 could still read the files.

    Moral of the story, don't mess with the dedup hack for Windows 8 unless you want to put all your data at risk. I came away lucky!

  5. I'm getting the same exact issue on one duplicate drive (seagate barracuda 2TB) that stopped working on me in my HP Media Server 485. I had two identical drives in two of the four bays. The OS was WHS 2003. Health status was flashing blue so I removed the drives and checked them through a USB drive enclosure into my desktop running Win7 Pro 64x. And I tried it on my laptop running win 8. The main drive with the OS (HP) was locked up and wouldn't respond. The top drive acts normal and shows me the files and values. However any attempt to view or transfer data gives me the issues the other users are having and the same error code. Any suggestions for my issue? -rob


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