What is a shadow copy?

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

A shadow copy, also referred to as a snapshot, is a point-in-time copy of a replica stored on the Data Protection Manager (DPM) server. A replica is a complete point-in-time copy of the protected shares, folders, and files for a single volume on a file server. To start data protection, a full replica of the selected data must be copied to the storage pool on the DPM server. Thereafter, the replica is periodically synchronized with changes to the protected data. DPM creates shadow copies of each replica in a protection group according to a specified schedule. You can access the shadow copies to recover previous versions of files in the event of data loss or corruption. You can recover data and you can also enable end-user recovery so that end users can recover their own data.

If the DPM server has adequate storage space, DPM can store a maximum of 64 shadow copies per protection group. When storage area limits have been reached and a new shadow copy is created, the oldest shadow copy is automatically deleted and cannot be restored. When you select shadow copy times, DPM provides you with estimates for recovery range and maximum data loss. These estimates will help you specify a shadow copy schedule that provides adequate data protection and meets your recovery goals. A maximum of 8 shadow copies can be scheduled per day.