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What are the components of latency and drive performance?

April 26, 2017components drive latency PERFORMANCE

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What are the components of latency and drive performance?

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A. The components of disk performance are seek and rotational latencies, SCSI command I/O and processing overhead, data transfer time and main operating system I/O software overhead. In an SSD, seek and rotational latencies are fixed, and represent to software overhead necessary to setup a data transfer. Data transfer time varies with the length of the IO transfer being performed. For shorter data transfers, seek and rotational latencies play a more important role in I/O transfer rate. For long data transfers, the SCSI IO bandwidth can approach that of the SCSI bus bandwidth (currently 80MB/sec for Curtis products). SCSI bus bandwidth also plays an important role with SSD technology. Competitive SSDs with slower Fast-20 and Ultra 40MB/sec bus bandwidths will pay a significant performance penalty, because data can be moved from the SSD to the Host system two to four times faster with Curtis Ultra2-80MB/sec SCSI interface.