Of course your restore won't work if backup is not.  However, in my case backup does not fail - it just won't backup specific files.  Here is the situation: we use Honeywell Uniformance PHDServer which has its own structure and one of the most important folders is called - Archive.  So, imagine structure like this:

E:\Uniformance\PHDServer\Archive and some idx and dat files inside.  Now, one usually does scheduled backup and get's all green and forgets about it.  So did I.  Then restore request came today since disk failed and everything was restored except content of this Archive folder. 

I checked mminfo and size of E drive was rather small so I was quite sure I never backed up this.  Then I checked another host with same setup and found that data is there, but not backed up under E save set.  So, I thought, it must be some VSS SYSTEM saveset and did nsrinfo search - but it is not there at all. Great, so we have everything except perhaps most important data on the box. Let's do manual backup... guess what:

E:\Uniformance\PHDServer\Archive>save -s SERVER -b POOL SCAN00001.dat save: E:\Uniformance\PHDServer\Archive\SCAN00001.dat  0 KB 00:00:32      0 files 7167:save: save completion time: 15-2-2013 16:37:09

Above file is 4GB - but bloody thing will always finish soon with 0KB saved.  Why!?  So, I did -D9 - but I do not see anything inside to ring the bell.  There is no directive assigned to this host, client side or server side, nothing.  It's funny, when you go to GUI and you select file it starts to run, asks for pool and then says - 0KB saved. Before you ask, this is local disk data - no DFS or any other mumbo jumbo.

I did however another test which is also sort of interesting:

• created E:\H folder and copied SCAN00001.dat file there
• backup process against E:\H\SCAN00001.dat works fine
• created folder Archive and moved SCAN00001.dat to that folder
• backup process against E:\H\Archive\SCAN00001.dat works fine
• created folder PHDServer and moved Archive to that folder
• backup process against E:\H\PHDServer\Archive\SCAN00001.dat works fine
• created folder Unifomance and moved PHDServer to that folder
• backup process against E:\H\Uniformance\PHDServer\Archive\SCAN00001.dat works fine

So, from here I see 3 possible outcomes:

• there is some wierd registry setting which instructs these files not to be backed up ever - not sure if such thing exists in first place and I certainly do not see it from debug CLI log
• there is exotic and exclusive lock on files breaking VSS/save the way it does - not sure only why Explorer is able to copy the file without any issues
• there is a bug with software - namely NetWorker

It might be something else, but this little thing took my afternoon and most likely will take away rest of the weekend.  Did anyone had experience with events like this before or has some starting point to check against?  The affected system is win2k8 R2 running 7.6.3.6 client.