Single Server Model

Single Server Model

As opposed to the direct connection model, this type of setup is based on a backup server, connected through a network to the machines that will need to take a backup. These machines are often referred to as clients or agents.

The tape device (or other storage media) will be connected to this backup server (see Figure 5). The advantages of this design are that centralized storage administration is possible and the number of storage devices is reduced (and probably the cost).

However, the problem here could be the network bandwidth. Since all data that is backed up needs to go over the network, the throughput is smaller than what we have using a direct tape connection. Every client that is added will need some of this bandwidth (see Network Bandwidth Considerations). This bandwidth issue becomes even more important when dealing with a distributed site. Let's imagine that one of the machines that needs to be backed up is located in a different location than the backup server, with only a very slow link between these two sites. Throughput could diminish in such a way that it would take longer than 24 hours to back up the remote system. In this case, a two-tier solution would be better.

Another disadvantage is that the machine used as backup server should be a dedicated machine. The reason for this is that backup and restore operations would have an impact on this server's performance. If you included it in the regular server pool, it could slow down all operations on the network servers.

•  For example, network bandwidth is not unlimited.
•  Another reason for the  limit on clients that a single server will support is that each session  will use resources (processor, memory) on the backup server.

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