Allocating Space for Protection Groups

Published : April 8, 2005 | Updated : August 17, 2005

When you create a protection group, you must allocate space on the storage pool for the replicas, shadow copies, and transfer logs for each volume that you have selected for inclusion in the group, and you must allocate space on the file servers for the synchronization logs for each of the selected volumes.

DPM provides default space allocations for the volumes in the protection group. Table 3.1 shows how DPM calculates the default allocations.

Table 3.1   How DPM Calculates Default Space Allocations for Volumes

We recommend that you accept the default space allocations unless you are certain that they do not meet your needs. Overriding the default allocations can result in allocation of too little or too much space.

Allocation of too little space for the shadow copies can prevent DPM from storing enough shadow copies to meet your recovery range objectives. Allocation of too little space for the synchronization log can result in an overflow of the log, which necessitates a consistency check. Allocation of too much space wastes disk capacity.

If, after you have created a protection group, you discover that you have allocated too little space for a volume in the protection group, you can increase the allocations for the replica, shadow copies, and synchronization log for each volume.

If you discover that you have allocated too much space for the protection group, the only way to decrease allocations for a volume is to remove the volume from the protection group, delete the replica of the volume, and then add the volume back to the protection group with smaller allocations.