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Re: [rdiff-backup-users] native VSS (Shadow Copy) support

From: Dominic Raferd
Subject: Re: [rdiff-backup-users] native VSS (Shadow Copy) support
Date: Tue, 06 Apr 2010 18:27:20 +0100
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv: Gecko/20100317 Thunderbird/3.0.4

On 06/04/2010 17:03, Greg Freemyer wrote:
On Tue, Apr 6, 2010 at 11:27 AM, Randy Syring<address@hidden>  wrote:
Josh Nisly wrote:
Two things:
1) The rdiff-backup project likely won't accept patches for features that
are platform specific. There are exceptions for OS-specific filesystem
metadata, but VSS doesn't fall into that category.
Now that there is consideration of restarting development, any chance we
could reconsider this?  Any backup solution has to wrestle with the Windows
user base and the key issue on Windows is whether or not a backup solution
uses VSS.  If rdiff-backup supported VSS, its uptake might be huge.

At very best, maybe a plugin system so that VSS can be added easily without
needing to touch the core code?
I don't post here often, but I strongly agree that snapshot technology
should be leveraged by the rdiff-backup environment.

I'm not as positive that it needs to be in the tool itself.  I can't
remember the name of the package, but I believe there is a linux
package that wraps rdiff-backup and uses LVM snapshots from which it
runs rdiff-backup.

As to VSS, it is supported in Windows XP SP3, 2003, Vista, 2008, etc.
  So it is a long term technology that it here to stay.

To me the only thing to really discuss is how vss support should be
integrated into a windows rdiff-backup environment, not if it should

2) I've written a python extension module in C++ to implement VSS. Is that
something that you'd be interested in?
Very, please share.  Have you integrated this with rdiff-backup at all?
The great thing about C code, etc. (as opposed to just scripts calling
the Vista provided CLI commands) is that VSS CLI commands are not
included in XP SP3 iirc.  And also with XP SP3 you only have 20 or 30
seconds to mount the VSS snapshot after you initialize it.  (again,

So having it in a real program as opposed to just a script makes it
easier to have the error / retry logic built in.

And for those that don't know much about VSS snapshots, one really
cool feature is that services like Exchange, MS-SQL, etc. have vss
knowledge integrated into them.  They register themselves with the vss
service and whenever a snapshot is created, the registered services
are notified to quiesce themselves prior to the snapshot being made.

I don't know if people are backing up that class of service via
rdiff-backup, but if they are it is pretty critical that vss snapshots
be used in order to ensure you have quiesced data.

vss also solves the open file issue that is so problematic with windows backups.

Thanks for reading
I have a Windows utility called TimeDicer (www.timedicer.co.uk) which is a wrapper for rdiff-backup, backing up from Windows to Linux, and it uses VSS. So it is not essential to have VSS built into rdiff-backup, even though it would be nice.


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