Choosing a Replica Creation Method
Published : April 8, 2005 | Updated : August 17, 2005
When you create a protection group, you must choose a method for creating the replicas for the volumes included in the group. Replica creation involves copying all the data selected for protection to the DPM server and then running synchronization with consistency check for each of the replicas.
DPM can create the replicas automatically over the network, or you can create the replicas manually by restoring the data from removable media such as tape. Automatic replica creation is easier, but, depending on the size of the protected data and the speed of the network, manual replica creation can be faster.
To help you choose a replica creation method, Table 3.2 provides estimates for how long DPM takes to create a replica automatically over the network given different protected data sizes and network speeds. The estimates assume that the network is running at full speed, and that other workloads are not competing for bandwidth. Times are shown in hours.
Table 3.2 Hours to Complete Automatic Replica Creation at Different Network Speeds
Size of Protected Data |
512 Kbps |
2 Mbps |
8 Mbps |
32 Mbps |
100 Mbps |
|---|---|---|---|---|---|
1 GB |
6 |
1.5 |
< 1 |
< 1 |
< 1 |
50 GB |
284 |
71 |
18 |
5 |
1.5 |
200 GB |
1137 |
284 |
71 |
18 |
6 |
500 GB |
2844 |
711 |
178 |
45 |
15 |
If you are deploying DPM to protect data over a WAN, and your protection group includes more than 5 GB of data, we strongly recommend that you choose the manual method for creating the replicas. |
.gif)
Considerations for protecting data over a WANAutomatic Replica Creation
For large replica creation jobs, you may want to schedule the job to run only during periods of light network traffic. Although you cannot directly schedule replica creation jobs to run in sessions, you can achieve the same effect by converting the replica creation job into a daily consistency check job. After you convert the job, DPM will complete the creation of the replicas as part of the consistency check.
To convert a replica creation job into a consistency check, start automatic replica creation, cancel the job, and then schedule a daily consistency check for the protection group. Specify the start time and duration of the operation for the period during which you want the job to run. If the consistency check exceeds the duration that you have specified, it pauses at a check point, and then automatically restarts from the check point at the start time on the following day. You can also manually restart a paused consistency check at any time.
Manual Replica Creation
If you choose manual replica creation, DPM specifies the precise locations on the DPM server where you must create the replicas. Typically, you create the replicas by restoring your most recent backup of the file server data from removable media such as tape. After you restore the data, you complete the process by running synchronization with consistency check for each of the replicas.
It is crucial that when you restore the data, you retain the original directory structure and properties of the source data, such as time stamps and security permissions. The more discrepancies that exist between the replicas and the protected source data, the longer the consistency checking part of the process takes. If you do not preserve the original directory structure and properties, manual replica creation can take as long as automatic replica creation.
For step-by-step instructions for restoring backups using common backup applications, see the following white papers: