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Voblin
Joined: 18 Jan 2011
Posts: 4
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 Posted: Tue Jan 18, 2011 11:48 pm Post subject: Win XP: CRC comparison does not work for open PST |
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Hello,
I am evaluating VV Pro 2.5 (Build 2501) on Win XP SP3. While trying different backup scenarios I ran into something that might be a potential problem for me.
I will be running a backup on a standalone PC. Being a "belt and braces" type, I would like VV to use CRC comparison while working out which files need backing up - just to make sure that my backup hasn't gone bad. Here is my profile:
| Quote: |
Comparison
- Comparison Type: CRC (CRC calculated on entire file)
Execution
- Method: Backup (Mirror Source to Target)
- No overwrite / read-only / error confirmations
- No archive for deleted/replaced source files
- No archive for deleted/replaced target files
- Copy files even if timestamp changes after initial comparison
- Try to copy files that are in use by other applications
- Use 'Volume Shadow Copy' to copy open files for source
- Detailed Volume Shadow Copy log level
- Copy file/folder permissions
- Verify successful file copy by checking file CRC
- Replace newer target files with older source files (backup only) |
The problem happens on the open PST (Outlook) file. If there is no need for CRC comparison prior to copy (when the target isn't there) - everything works fine, including CRC verification. However, when VV needs to do CRC comparison _prior_ to copy - here is what I get in the log:
| Quote: | | [ERROR] ERROR: some data from file "xxx.pst" could not be read. File may be in use by another application, it may be incorrectly stored on media or, if compressed/encrypted, it may contain errors. File will be excluded from comparison/execution. |
Q1. From the log file, I can see that Volume Shadow Copy gets initialized as 1st step of the execution stage. Doesn't it need to be initialized earlier, at the comparison stage, so that CRC can be calculated for a file that is open?
Q2. I suppose, a workaround would be to create a separate profile specifically for the Outlook file, and in this profile not use CRC comparison. If I go this way - how do I force VV to always copy the PST file? What I want to avoid is the (possibly unlikely) scenario when the timestamp on the backup file looks the same as on the source, but the backup file got corruped somehow. Forcing the overwrite with subsequent verification should resolve this.
I would appreciate your advice.
Last edited by Voblin on Wed Jan 19, 2011 11:26 am; edited 1 time in total |
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TGRMN Software
Site Admin
Joined: 10 Jan 2005
Posts: 8759
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| Posted: Wed Jan 19, 2011 10:23 am Post subject: |
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Hi,
the issue is that on XP the option to create the snapshot during comparison (instead of during copy) is not available.
I suggest you create a separate job for the PST file without CRC comparison. You can force copying the PST each time in profile settings -> comparison in ViceVersa PRO 2.5
thanks
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Voblin
Joined: 18 Jan 2011
Posts: 4
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| Posted: Wed Jan 19, 2011 10:52 am Post subject: |
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Thank you for the prompt reply.
Just out of interest - is this behaviour under XP caused by some kind of technical limitations of VSS implementation XP itself? And if not - are there any plans for future versions of VV to change it so that CRC comparison for open files would be possible? |
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Voblin
Joined: 18 Jan 2011
Posts: 4
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| Posted: Wed Jan 19, 2011 11:24 am Post subject: |
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One more question please - to the best of your knowledge, in my scenario (XP SP3, backup, local files to an external SATA disk connected via USB 3.0) - what other kinds of open files/running applications might cause problems:
1. during CRC comparison (before execution)
2. during CRC validation (after execution)
Thank you for your help.
PS. I will change the subject of my first post - hopefully it might help others with the same problem find the solution faster... |
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Voblin
Joined: 18 Jan 2011
Posts: 4
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| Posted: Wed Jan 19, 2011 4:58 pm Post subject: |
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Sorry, one more thing. This is only the way I found of forcing execution on a PST:
| Quote: | - Exclude files: "*.*"
- Include files: "name.pst"
- Comparison Type: Size and Timestamp
- Files with these extensions are always newer in source: *.pst |
Does this look right to you? Or is there a more elegant way? |
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TGRMN Software
Site Admin
Joined: 10 Jan 2005
Posts: 8759
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| Posted: Thu Jan 20, 2011 10:38 am Post subject: |
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Hi,
| Quote: | | Just out of interest - is this behaviour under XP caused by some kind of technical limitations of VSS implementation XP itself? And if not - are there any plans for future versions of VV to change it so that CRC comparison for open files would be possible? |
It's a limitation of XP.
| Quote: | 1. during CRC comparison (before execution)
2. during CRC validation (after execution) |
1. The CRC comparison can have a problem if a file is open during backup by another application.
2. None if Volume Shadow Copy is activated (after comparison the shadow copy is used).
| Quote: | - Exclude files: "*.*"
- Include files: "name.pst"
- Comparison Type: Size and Timestamp
- Files with these extensions are always newer in source: *.pst
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- Exclude files: "*.*" is not needed but does not harm (if only 1 include filter is present VV excludes all other automatically. Now that you do not use CRC you can activate Volume Shadow Copies
thanks
_________________
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TGRMN Software Support
http://www.tgrmn.com
http://www.compareandmerge.com |
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