Seagate ST373207FC Cheetah 10K.7 FC Product Manual - Page 25

Flaw reallocation performance impact (for flaws reallocated at format time using the spare sectors per sparing zone reallocation scheme.) Overhead time for head switch in sequential mode Overhead time for one track cylinder switch in sequential mode Average rotational latency Negligible 0.8 msec 1.2 msec (typical) 3.0 msec *Assumes no errors and no relocated logical blocks. Rate measured from the start of the first logical block transfer to or from the host. Notes for Section 4.2. [1] Execution time measured from receipt of the last byte of the Command Descriptor Block (CDB) to the request for a Status Byte Transfer to the Initiator (excluding connect/disconnect). [2] Typical access times are measured under nominal conditions of temperature, voltage, and horizontal orientation as measured on a representative sample of drives. [3] Assumes system ability to support the rates listed and no cable loss. [4] Access to data = access time + latency time. 4.3 Start/stop time If the Motor Start option is disabled, the drive becomes ready within 25 seconds after DC power is applied. If a recoverable error condition is detected during the start sequence, the drive executes a recovery procedure and the time to become ready may exceed 25 seconds. Stop time is less than 30 seconds (maximum) from removal of DC power. If the Motor Start option is enabled, the internal controller accepts the commands listed in the Fibre Channel Interface Manual less than 3 seconds after DC power has been applied. After the Motor Start command has been received, the drive becomes ready for normal operations within 25 seconds (excluding the error recovery procedure). The Motor Start command can also be used to command the drive to stop the spindle. There is no power control switch on the drive. 4.4 Prefetch/multi-segmented cache control The drive provides a prefetch (read look-ahead) and multi-segmented cache control algorithms that in many cases can enhance system performance. Cache refers to the drive buffer storage space when it is used in cache operations. To select this feature, the host sends the Mode Select command with the proper values in the applicable bytes in page 08h. Prefetch and cache operations are independent features from the standpoint that each is enabled and disabled independently using the Mode Select command; however, in actual operation, the prefetch feature overlaps cache operation somewhat as described in sections 4.5.1 and 4.5.2. All default cache and prefetch mode parameter values (Mode Page 08h) for standard OEM versions of this drive family are given in Table 27. 4.5 Cache operation Note. Refer to the Fibre Channel Interface Manual for more detail concerning the cache bits. Of the 8,192 kbytes physical buffer space in the drive, 6,991 kbytes can be used as a cache. The buffer can be divided into logical segments (using Mode Select Page 08h, byte 13) from which data is read and to which data is written. Cheetah 10K.7 FC Product Manual, Rev. D 13