How is the MongoDB backup snapshot transferred from Ops Manager to file system store?
As per MongoDB documentation here Ops Manager creates backups of MongoDB replica sets and sharded clusters. After an initial sync, Ops Manager tails the operation log (oplog) to provide a continuous backup with point-in-time recovery of replica sets and consistent snapshots of sharded clusters.

Why doesn’t the Backup feature support standalone deployments?

After an initial sync of your data, Ops Manager copies data from the oplog to provide a continuous backup with point-in-time recovery. Ops Manager does not support backup of standalone servers, which do not have an oplog. To support backup with a single mongod instance, you can run a one-member replica set.

How can I use Backup if Backup jobs fail to bind?

The most common reason that jobs fail to bind to a Backup Daemon is because no daemon has space for a local copy of the backed up replica set.

To increase capacity so that the backup job can bind, you can:


add an additional backup daemon.
increase the size of the file system that holds the Head
directory.
move the Head database data to a new volume with more space, and
create a symlink or configure the file system mount points so that
the daemon can access the data using the original path.