Long time pre-processing

[Jungle_Tech]

Windows Server 2008 R2 running BE2012 SP2 as a VM (esx5.1).

Target machines are Win2008R2, VM's, Vmtools installed, RAWS installed, backed up as a VM through vCentre. 

Only a handful of my 50+ servers seem to have an issue with pre-processing for a very long time. For example, I have an exchange server (2010 sp2) at the moment that has been pre-processing for an hour and a half and counting. Other exchange servers (2010 sp2) dont have this problem. I also have this problem with 1 file server but not others. These handful of problem vm's are spread across different sites, BE servers, VM clusters....as a test, I did disabled GRT on one of them and it seemed much quicker, but obviously I need GRT enabled. 

Suggestions please? 

[pkh]

Are these problem servers very busy during the time of the backup?  If so, then BE will need time to acquiese them and take a snapshot.

[Jungle_Tech]

I did suspect it was related to quiescing, and it might make sense for the exchange servers. But one of the file servers experiencing this problem supports maybe 10 users at the moment. Its not high use, although does have hundreds of GB of data. 

[Jungle_Tech]

Some more info to fuel the discussion - the small file server mentioned previously has now been pre-processing for 4 hours and counting. It has maybe 10-20 files open from network users. 

Why so long?