Bandwidth (BW) is generally referred to the amount of data read/write storage system can handle in one second (in MB/s or GB/s units), demonstrating the capability of storage system in handling sequential requests. The storage bandwidth is a function of the bandwidth of disk array, internal interconnections (such as interconnections between controllers and disk subsystem), and external connections (such as connection between storage system and hosts). The highest bandwidth usage is observed when the requests are sequential with big size (as an example we can note multimedia applications). Storage manufacturers report the storage bandwidth for the sequential big requests that can use the maximum storage bandwidth. In practice, however, the bandwidth may be lower than the reported bandwidth depending on the workload characteristics.

Number of transactions per second, known as IOPS, stands for the number of IO operations the storage system can accomplish in one second. IOPS directly depends on workload characteristics such as request size and randomness. When using HDDs, workloads with small and random request result in comparably lower IOPS. An HDD can ideally handle 200 to 300 random requests per second. Using RAID configurations, the IOPS for random requests can increase to 500 and 600. Nowadays, many applications such as banking and social networks desire 30,000 to 50,000 IOPS that cannot be provided just by RAID mechanism, mandating more advanced mechanisms such as caching.

Average response time, usually reported in milliseconds (ms), is defined as the aggregation of time a request sent to SAN storage, queued, and finally served. It is notable that if the response delay surpasses a predefined value, the client system considers it as a request failure. Average response time is in direct relationship with the rate of requests and increases by the increase of request queue. A high average response time can decreases service quality and user satisfaction.