IBM DTTA-351010 Hard Drive Specifications - Page 17

3.3 Performance Characteristics A file performance is characterized by the following parameters: Command Overhead Mechanical Positioning − Seek Time − Latency Data Transfer Speed Buffering Operation (Look ahead/Write cache) Note: All the above parameters contribute to file performance. There are other parameters that contribute to the performance of the actual system. This specification tries to define the bare file characteristics, not the system throughput which will depends on the system and the application. 3.3.1 Command Overhead Command overhead is defined as the time required: from the command is written into the command register by a host to the assertion of D R Q for the first data byte of a READ command when the requested data is not in the buffer exclude − Physical seek time − Latency time Command Type (File is in quiescence state) Read(Cache not hit) (from Command Write to Seek Start) Read(Cache hit) (from Command Write to DRQ) Write (from Command Write to DRQ) Seek (from Command Write to Seek Start) Figure 3. Command Overhead Note: The above table gives an average time. Time(Typical) 0.60 msec 0.10 msec 0.015 msec 0.50 msec Time(Typical) for Queued command 0.60 msec 0.10 msec 0.01 msec Not applicable 3.3.2 Mechanical Positioning 3.3.2.1 Average Seek Time (Without Command Overhead, Including Settling) Command Type Read Write Figure 4. Mechanical Positioning Performance Typical 8.5 msec 9.5 msec Max 9.5 msec 10.5 msec "Typical" and "Max" are given throughout the performance specification by; Typical Average of the drive population tested at nominal environmental and voltage conditions. Drive Characteristics 9