Re: [Bacula-users] VSS enable windows client

[Kern S. <ke...@si...>]

Hello,


On 11/16/2015 07:17 AM, Konstantin Khomoutov wrote:
> On Mon, 16 Nov 2015 14:55:04 +0000
> "More, Ankush" <ank...@ca...> wrote:
>
>> We are taking backup of windows client with VSS enable.
>> Is it mandatory to take  NTBackup to backup the system state
>> separately, for successful ( with all windows services) restoration
>> of client backup.
> Yes.
> I've just recently tried to explain what VSS is all about to another
> person here on this list [1].  Please consider reading that post.
>
> 1. http://sourceforge.net/p/bacula/mailman/message/34618032/

Everything that this link says is correct, however it does not give a
full explanation of the problem. When Bacula backs up a VSS snapshot, if
you specify to backup all the hard disks, it will in fact correctly
backup everything about the system state.  The problem comes in the
restore: when Windows is running as it is with a normal restore, unlike
Linux/Unix systems, you cannot overwrite many of the main system files
(system state) because they are in use by the Windows OS.  So to fully
restore the system state, you must have special code that restores the
system state files to an alternate location, then when you reboot the
system following that restore, the Windows OS will replace the files for
you. 

The code to put the system files in special locations is very
complicated and is not part of the standard Bacula.  If I am not
mistaken it is part of NTBackup which can restore the system state, and
obviously, it is part of the Bacula Enterprise Windows BMR tool.

The same issue comes up for applications.  If you try to restore a file
that is in use, the Windows OS will not let you.  The solution is far
simpler than the problem with the Windows system files, because you can
simply stop the application (no files being used), restore the files,
then restart the application.  Or if you have a special plugin that
knows how to work with the application, many applications (especially
ones such as MSSQL and Exchange) permit hot-restore of their files, but
of course, hot-restore is very complicated as is restoring Windows
system state files.

Best regards,
Kern