My updated list of tips, if you run into Exchange 2010 backup challenges:
1) Increase the DAG heartbeat time (no reboot needed) to avoid cluster failover
cluster /prop SameSubnetDelay=2000:DWORD
cluster /prop CrossSubnetDelay=4000:DWORD
cluster /prop CrossSubnetThreshold=10:DWORD
cluster /prop SameSubnetThreshold=10:DWORD
2) Use new Veeam Storage Snapshot Feature (Lefthand/3PAR/VSA) if you can (after v7 release) => Reduces Snapshot Lifetime to some seconds => No load and problems at commit because of less data.
3) If you have problems with cluster failover at Backup, one option is to backup DAG member(s) that hold only inactive databases (no cluster failover because of no active databases) (Logfile Truncation will be replicated by Exchange in whole DAG)
4) To reduce Snapshot commit time (and to reduce data in the snapshot), try to avoid any changes at the backup time window (User, Background processes, Antivirus, ....). Also try to avoid that on all LUNs on the storage System itself (faster writes at snapshot commit).
5) If you can not avoid many changes on block level at your backupwindow? Use Forward Incremental or if you need space Forward incremental with daily transform into rollbacks. Reverse Incremental took a bit longer than the other backup methods => longer snapshot livetime => more changes in the Snapshot to commit
6) To reduce Snapshot lifetime and reduce amount of data to snapshot commit, use new parallel processing with enought ressources to backup all of your disks at the same time (after v7 release)
7) To reduce backup time window and snapshot lifetime, use Direct SAN Mode with minimal needed disks connected at selected Proxy. If not possible use NBD mode with 10GbE. (Do not run Proxy in Autoselect mode). Disable VDDK Logging for Direct SAN Mode if your backups themself run stable (ask support for the registry key and consequences).
8 ) Use actual VMware Versions (newest VADP/VDDK Kits with a lot of updates in it) and actual Veeam Versions (newer VDDK Integration)
9) Use at Minimum VMware vSphere 5.0 because of changes in the snapshot places and Background things.
10) If you still facing problems, use faster disks for all of the VM disks (also the OS disk!!!)
11) Less VM disks can help to reduce snapshot creation (and commit?) time.
12) To avoid VSS timeouts (hardcoded 20 seconds at Exchange VSS writer), Check your vcenter load and optimize it (or use direct ESX(i) Connections for Veeam VM selection, so that the snapshot creation took less time.
13) If you facing VM downtime because of Snapshot commit, maybe another Option (unsupported from VMware) is to change VM Setting snapshot.maxConsolidateTime = "1" (in sconds) (see discussion above).
14) If you see Exchange VSS Timeout EventLog 1296 => Change Log setting => Set-StorageGroup -Identity "<yourstoragegroup>" -CircularLoggingEnabled $false
15) VSS Timeout Problems => Add more CPU/Memory to the VM