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I have implement my own application (probably using Volume Shadow Copy) for backing up the Exchange 2010 server.

I have found following schema: Backup Sequence Diagram

But I cannot find any functions for directly freeze/thawn the Exchnage Writers.

I did find only such functions that call "freeze" and "thawn" commands as part of snapshot creation (see following schema: Overview of Processing a Backup Under VSS)

Please help me to find any documentation about first schema, i.e. which API functions I can use to freeze and thaw Writers

Thanks

Oleg Kalenchuk
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1 Answers1

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There is a comprehensive example, in the form of VSHADOW.exe which is a sample VSS Requestor provided as part of the SDK.

The license agreement includes this:

Sample Code. You may modify, copy, and distribute the source and object code form of code marked as “sample.”

You may be able to adapt VSHADOW to do what you want, however the simplest way is to use VSHADOW.exe as is.

You can use VSHADOW to create the shadow copy, mount it on a symbolic link or drive letter, do whatever it was you wanted, then destroy the shadow copy volume and symlink.

To be clear, you are not supposed to back up the frozen files during the freeze action, you are supposed to create a shadow copy of the frozen files, so they can be unfrozen quickly, and then back up the shadow copy.

VSHADOW will freeze, create a shadow copy, unfreeze (taking only a few seconds in all), then mount the shadow copy on a drive letter, call an external program - your backup program, which can then back up the shadow copy of the exchange database - then delete the shadow copy. The shadow copy will not change, and can be backed up without causing sharing conflicts.

Ben
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  • I investigated sources of VShadow application and I have found only one function that may be helpful for me in this task. This is a "SimulateSnapshotFreeze" function. But I cannot find any documentation about this function, I know only that it is implemented in the "vssapi.dll" library. Unfortunately the VShadow.exe is not comprehensive example :((( – Oleg Kalenchuk Mar 07 '13 at 12:38
  • @OlegKalenchuk, you are not supposed to back up the files during the freeze, you are supposed to just create a shadow copy of the frozen files, so they can be unfrozen quickly, and then back up the shadow copy. – Ben Mar 07 '13 at 13:53
  • Thank you, I guessed that I cannot freeze writers immediately. Does this mean that the "Backup Sequence Diagram" is incorrect (particularly at the step 11)? – Oleg Kalenchuk Mar 07 '13 at 14:10
  • @OlegKalenchuk, no, it's more likely that a random SO user like me is wrong than Microsoft's official documentation! I ***think*** it is just slightly different point of view. From the point of view of the VSS writer (Exchange) the backup is complete once the Shadow Copy is created. From the point of view of the backup application, you then have to copy the data in the shadow copy to some other media. However I am not an expert on backup technologies in general or VSS in particular, just someone who has dabbled a bit. By the time you have finished you will know a lot more about it than me! – Ben Mar 07 '13 at 15:33