Free tutors on Back-up server and application server on the same physical computer
The third possible way of increasing performance is to install the back-up server and application server on the same physical computer (Figure 7.6). This results in the back-up client also having to run on this computer. Back-up server and back-up client communicate over Shared Memory (Unix), Named Pipe or TCP/IP Loopback (Windows) instead of via LAN. Shared Memory has an infinite bandwidth in comparison to the buses, which
means that the communication between back-up server and back-up client is no longer the limiting factor. However, the internal buses continue to get clogged up: the back-up client now loads the data to be backed up from the hard disk into the main memory via the buses. The back-up server takes the data from the main memory and writes it, again via the buses, to the back-up medium. The data is thus once again driven through the internal bus twice. Tape reclamation and any copying operations within the storage hierarchy of the back-up server could place an additional load on the buses. Without further information we cannot more precisely determine the change to the CPU load. Shared Memory communication (or Named Pipe or TCP/IP Loopback) dispenses with the CPU-intensive operation of the network card. On the other hand, a single computer must now bear the load of the application, the back-up server and the back-up client. This computer must incidentally possess sufficient main memory for all three applications. One problem with this approach is the proximity of production data and copies on the back-up server. SCSI permits a maximum cable length of 25 m. Since application and back-up server run on the same physical computer, the copies are a maximum of 50 m away from the production data. In the event of a fire or comparable damage, this is disastrous. Therefore, either a SCSI extender should be used or the tapes taken from the tape library every day and placed in an off-site store. The latter goes against the requirement of largely automating data protection.
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