Computer Associates BABNWUP900NE6 Administration Guide - Page 87

Multiplexing ■ Each slave job has a default job description with this pattern: MULTISTREAM[JOB[MID]]SUBJOB[SID] where MID is the master job ID and SID is the sub job (slave job) ID. ■ The multistreaming option is ignored if the groups you choose have only one device, or if only one object (volume, database, or remote node) backup is submitted. Note: You should use the same types of tape devices for multistreaming jobs. In order to achieve the optimum performance with your multistreaming jobs, you should use a high-end server machine with multiple processors and at least 256 MB memory per processor. Multiplexing Multiplexing is a process in which data from multiple sources is written to the same media simultaneously. When a job that has multiple sources is submitted with the multiplexing option enabled, it is broken into child jobs-one for each source. These child jobs write data to the same media simultaneously. Note: When using multiplexing, you can select the maximum number of streams that can write a tape at the same time. For more information on this setting, see the section Multiplexing Global Options in this chapter. Multiplexing is useful when your tape drive throughput is faster than the rate at which data can be extracted from the source. Factors that can affect backup throughput are as follows: ■ The kind of data being backed up. For example, backing up large number of small files reduces backup throughput because of the larger number of necessary file system operations (file open and close). ■ Some databases may be inherently slow in providing data. ■ The network throughput of the server being backed up. ■ The disk performance on which the data resides. ■ The server resources like CPU speed, memory size, page file size, network card, and amount of other activities on the server. ■ Network backups that involve hundreds of servers. Backing Up Data 3-25