Storage Networking Performance

摘要

Performance is the result of complex interactions that take place among numerous system components. Therefore, it is difficult to quantify it with a few simple numbers. The following sections define and explain several metrics commonly used in the performance analysis of storage systems. The overall performance of a system or a component is a combination of many of these metrics. Table 1-1 shows the units of magnitude commonly used in many of the metrics. One confusing point often found in the computing literature is whether the units represent powers of 10 or powers of 2. For example, in many contexts, K (kilo) denotes a thousand (1 x 10~3) and in others it denotes 1,024 (1 x 2~(10)). Unfortunately, the terminology still hasn't been consistently defined. The symbols K, M, G, T, P, and so on, denote powers of 1,000 when they are applied to measurements of bandwidth and powers of 1,024 when they are applied to measurements of storage capacity. For example, a transmission line can have a bandwidth of 1.5 Mbps (1,500,000 bps), and a read buffer can have a capacity of 4KB (4,096 bytes).