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The same Exchange 2010 database restored from disk then tape has different MD5 hash? RRS feed

  • Question

  • I've noticed the following, so I'm asking if anyone else has done this test and whether they can reproduce these results.

    Here's what I did:

    1. create a short term express-full recovery point using disk, of an Exchange 2010 mailbox database.
    2. when complete perform a long term to tape recovery point of the same database.
    3. view the recovery points for the database in the restore tab, notice that two points exist, eg:
    3:30 PM(Disk)
    3:30 PM(Tape)
    4. perform a restore to folder of each recovery point, using different target folders, configured to not perform any ESEUTIL clean-ups etc.
    5. compare the .EDB file in each folder using an MD5 hash calculator, such as Microsoft's FCIV.EXE File Checksum INtegrity Verifier tool.
    6. notice that each supposedly identical copy of the .edb file has a different MD5 hash.

    The files are DIFFERENT! WHY?



    DPM 2012 4.0.1915.0
    • Edited by The Fellenator Tuesday, August 28, 2012 2:13 AM DPM 2012 4.0.1915.0
    Tuesday, August 28, 2012 12:58 AM

All replies

  • Hi,

    You said that you created short term express-full recovery point using Disk then long term to tape. This means that you created two different files for the same database. Its very small possibilty (not saying its impossible) to have two different files of getting two identical hashes.


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    Tuesday, August 28, 2012 5:59 AM
  • For protection groups configured for short-term-to-disk and long-term-to-tape; When you perform a long term recovery point to tape, it copies the last short-term disk copy (this is a static, unchanging, collection of files) to the tape.

    i.e. the data gets copied from a specific disk-based copy in the replica volume to the tape.  Specifically, it does't get another copy from the exchange server.

    You can watch this (on 2008R2) using resmon, during the short-term to disk, the exchange server is contacted and data flows from exchange to DPM, but the long term to tape it reads from the replica volume and writes that to tape.

    This is why I'm expecting the files to have bit-identical content when restored, and am surprised that they don't.



    Tuesday, August 28, 2012 6:29 AM
  • the original and the copied file should have the exact same MD5 Hash. The only explination for that is DPM is actually not copying but restoring DB from Disk to tape causing the creation og a new file thus why the new MD5 hash.


    Please remember to click “Mark as Answer” on the post that helps you. This posting is provided "AS IS" with no warranties. knowledge is valid only if it is shared by All.

    Tuesday, August 28, 2012 12:10 PM