Data Protection Manager (DPM) is the extension of Microsoft Backup, designed for the enterprise. It is based on volume shadow copies which create a ‘point in time’ snapshot of a Microsoft Volume. Microsoft provides the ability to take a full copy and then perpetual scheduled snapshots across a server and desktop environment. With DPM you can schedule and manage this activity centrally.
Shadow copies are dependant on a volume shadow copy writer in order to ‘quiesce’ the read/write activity to the volume to ensure data is consistent. Additional shadow copy writers have been written by Microsoft for applications such as SQL, SharePoint etc. Because the shadow copy writers are application aware they ensure the applications data is crash recoverable. The difference between crash consistent and crash recoverable is whether or not the data in transit is consistent with the data on the volume. If the snapshot is crash recoverable the data is consistent.
When snapshots are requested from the Hyper-V host level to take a point in time copy of a running virtual machines the snapshot is crash consistent. When it is initiated by the Operating system within the virtual machine using the application specific shadow copy writer the data is crash recoverable. This is why agents are typically run at both the Hyper-V host level and also within the virtual machines.
According to Microsoft the estimates for a single 2010 DPM server is as follows:
- 100 Servers
- 1000 Desktops
- 2000 SQL databases
- 40 TB Exchange Datastores
- Managing 80 TB of disk space