I've just started learning MongoDB, so hopefully this question won't be that trivial. My question is in regards to Ops Manager, in particular for backups. From what I understand, if I am backing up a source mongo database using Ops Manager, an "initial sync" is performed and copied to the Ops Manager application server. OpLogs are also copied over. From here on out, it seems that this "copy" (also called the "head" database) is used to create periodic snapshots that can be restored. So a few questions with this understanding:

1) The head database seems to reside on the application server using the "head directory" (i.e. mount-points/file systems) and am assuming is a live mongodb database?? Is that true? Or is it simply copied files that are not "up and running" in any way. In other words, do I need mongodb rpms/software installed on the Ops Manager application server as well? I'm assuming the head database is "live" (e.g. a hidden node in the replica set) as I am assuming the oplogs that are copied over are also applied to the head database so that periodic snapshots will be different. Again, is my understanding correct? 

2) If I configure 2 Ops Manager application servers (for HA purposes), I'm confused where the "head" database would reside (as that's put on a filesystem/directory - available to only a single server)? I realize the snapshots could exist on some shared storage (or even S3 storage, where we'd probably go with this), so it would be accessible anywhere. Does the head database also need to be on some shared block storage (e.g. NAS??). How does each application server work with the head database due to it being on block devices?

I will be opening a ticket with support on this as it is an Enterprise Mongo question that they can tackle. Thought I would ask the community first to see their thoughts.

Thanks in advance. 

Jim