Data Protection Manager (DPM), Microsoft's software for fast recovery of deleted or damaged files, needs storage space. Actually it needs two different kinds of storage space for the data entities it creates and uses. If the disk space is not properly allocated, DPM won't work properly.
When you set up a new protection group under DPM, the software will
recommend the amount of space to be allocated for storage. You should
generally accept the recommendation, keeping in mind that you may have
to increase the allocation later.
However, if you are only protecting part of the data on the protected
volume, you can use the DPM guidelines to calculate how much space you
will need for the different functions.
DPM needs storage in two different areas. One is the data storage
pool, which is the space DPM allocates for itself in the protected
storage pool. The second piece of storage DPM needs is space for the synchronization logs.
The pool is used for the replicas of the data DPM creates, as well as the transfer logs it uses to help manage those replicas.
Most of the data storage pool is given over to the replicas. The
replicas themselves need a minimum of 1.5 times the storage space of the data being protected. Note: This is a minimum. Based on your enterprise's patterns of use, you may need to add more space.
The next largest element in the data storage pool is the space allocated for the shadow copies. They should be allocated at least 20% of the space given to the replicas. Microsoft's recommended allocation for the shadow copies provides enough space for about two weeks worth of shadow copies. You can conserve disk space on the protected volume by setting aside less space for the shadow copies, but that means you will have fewer shadow copies, which can cause problems if data that is corrupt or deleted is not discovered for several days.
The data storage pool also stores the transfer logs DPM uses to keep up
with the synchronization logs. The transfer logs need a minimum of 1.4
times the size of the synchronization logs. Again, usage patterns may
indicate that you should increase this allocation.
The final piece of storage DPM needs is space for the synchronization
logs. Unlike the other three components, this is not in the DPM storage
pool; it is in the protected volume on the file server. It needs to be
at least 10% of the size of the protected volume.
For the past 20 years, Rick Cook has written about issues related to storage and storage management.
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