Know more how to get the opportunities for increasing performance on Several back-up servers

Know  more  how to get the opportunities for increasing  performance on Several back-up servers

Back-up is a resource-intensive application that places great demands upon storage devices, CPU, main memory, network capacity, internal buses and I/O buses. The enormous amount of resources required for back-up is not always sufficiently taken into account during the planning of IT systems. A frequent comment is 'the back-up is responsible for the slow network' or 'the slow network is responsible for the restore operation taking so long'. The truth is that the network is inadequately dimensioned for end user data traffic and back-up data traffic. Often, data protection is the application that requires the most network capacity. Therefore, it is often sensible to view back-up as the primary application for which the IT

infrastructure in general and the network in particular must be dimensioned. In every IT environment, most computers can be adequately protected by a network back-up system. In almost every IT environment, however, there are computers – usually only a few – for which additional measures are necessary in order to back them up quickly enough or, if necessary, to restore them. In the server-centric IT architecture there are three approaches to taming such data monsters: the installation of a separate LAN for the network back-up between back-up client and back-up server the installation of several back-up servers and the installation of back-up client and back-up server on the same physical computer (Section 7.7.3). 7.7.1 Separate LAN for network back-up The simplest measure to increase back-up performance more of heavyweight back-up clients is to install a further LAN between back-up client and back-up server in addition to the existing LAN and to use this exclusively for back-up (Figure 7.4). An expensive, but powerful, transmission technology such as ATM, FDDI or Gigabit Ethernet can also help here. The concept of installing a further network for back-up in addition to the existing LAN is comparable to the basic idea of storage networks. In contrast to storage networks, however, in this case only computers are connected together; direct access to all storage devices is not possible. All data thus continues to be passed via TCP/IP and through

application server and back-up server which leads to a blockage of the internal bus and the I/O buses. Individual back-up clients can thus benefit from the installation of a separate LAN for network back-up. This approach is, however, not scalable at will: due to the heavy load on the back-up server this cannot back up any further computers in addition to the back-up of one individual heavyweight client. Despite its limitations, the installation of a separate back-up LAN is sufficient in many environments. With Fast-Ethernet you can still achieve a throughput of over 10 MByte/s.The LAN technique is made even more attractive by Gigabit Ethernet, 10Gigabit Ethernet and the above-mentioned TCP/IP offload engines that free up the server CPU significantly with regard to the TCP/IP data traffic

 Several back-up servers

Installing multiple back-up servers distributes the load of the back-up server over more hardware. For example, it would be possible to assign every heavyweight back-up client a special back-up server installed exclusively for the back-up of this client (Figure 7.5). Furthermore, a further back-up server is required for the back-up of all other back- up clients. This approach is worthwhile in the event of performance bottlenecks in the metadata database or in combination with the first measure, the installation of a separate LAN between the heavyweight back-up client and back-up server.

The performance of the back-up server can be significantly increased by the installation of multiple back-up servers and a separate LAN for back-up. However, from the point of view of the heavyweight back-up client the problem remains that all data to be backed up must be passed from the hard disk into the main memory via the buses and from there must again be passed through the buses to the network card. This means that back-up still heavily loads the application server. The resource requirement for back-up could be in conflict with the resource requirement for the actual a application. A further problem is the realization of the storage hierarchy within the individual backup server since every back-up server now requires its own tape library. Many small tape libraries are more expensive and less flexible than one large tape library. Therefore, it would actually be better to buy a large tape library that is used by all servers. In a server- centric IT architecture it is, however, only possible to connect multiple computers to the same tape library to a very limited degree.