SAS I/O Performance

Many current systems employ Ultra 320 parallel SCSI for boot drives, local data storage, or external arrays of modest size. Systems emerging over the next two years will employ SAS disks for boot drives, local data storage, and external arrays of modest to large size. SATA makes use of the same SAS infrastructure and adds vast storage capacity at relatively low cost.

Two primary metrics of storage subsystem performance are data throughput and I/O rate. Data throughput is typically stated in terms of MB/s, and measures the maximum sustained data rate. Usually maximum data rates are seen with sequential data streams that are either entirely Read or entirely Write operations, and have data block sizes of 64 KBytes or larger. I/O rate is the maximum number of I/Os the system can complete per second.