Seagate ST39102LC Product Manual - Page 20
Cheetah 9LP Product Manual, Rev. C, Notes for Start/stop time, Prefetch/multi- - cylinders
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10 Cheetah 9LP Product Manual, Rev. C Sector Sizes: Default Variable 512 byte user data blocks 180 to 4,096 bytes per sector in even number of bytes per sector. If n (number of bytes per sector) is odd, then n-1 will be used. Read/write consecutive sectors on a track Yes Flaw reallocation performance impact (for flaws reallocated at format time using the spare sectors per sparing zone reallocation scheme.) Negligible Overhead time for head switch (512 byte sectors) in sequential mode Overhead time for one track cylinder switch in sequential mode Average rotational latency 0.8 msec 1.2 msec (typical) 2.99 msec 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 no errors and no sector has been relocated. [4] Assumes system ability to support the rates listed and no cable loss. [5] Access time = controller overhead + average seek time. Access to data = controller overhead + average seek time + latency time. 4.3 Start/stop time After DC power at nominal voltage has been applied, the drive becomes ready within 30 seconds if the Motor Start Option is disabled (i.e. the motor starts as soon as the power has been applied). If a recoverable error condition is detected during the start sequence, the drive executes a recovery procedure which may cause the time to become ready to exceed 30 seconds. During spin up to ready time the drive responds to some commands over the SCSI interface in less than 3 seconds after application of power. Stop time is less than 30 seconds from removal of DC power. If the Motor Start Option is enabled, the internal controller accepts the commands listed in the SCSI Interface Product 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 30 seconds typically (excluding an error recovery procedure). The Motor Start Command can also be used to command the drive to stop the spindle (see SCSI Interface Product Manual, part number 77738479). There is no power control switch on the drive. 4.4 Prefetch/multi-segmented cache control The drive provides prefetch (read look-ahead) and multi-segmented cache control algorithms that in many cases can enhance system performance. "Cache" as used herein refers to the drive buffer storage space when it is used in cache operations. To select prefetch and cache features the host sends the Mode Select command with the proper values in the applicable bytes in Mode Page 08h (see SCSI Interface Product Manual, part number 77738479. Prefetch and cache operation are independent features from the standpoint that each is enabled and disabled independently via the Mode Select command. However, in actual operation the prefetch feature overlaps cache operation somewhat as is noted in Section 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 Tables 8. 4.5 Cache operation In general, 840 Kbytes (3,700 kbytes of the 4,096 kbytes on units with this option) of the physical buffer space in the drive can be used as storage space for cache operations. The buffer can be divided into logical segments (Mode Select Page 08h, byte 13) from which data is read and to which data is written. The drive maintains a table of logical block disk medium addresses of the data stored in each segment of the buffer. If cache operation is enabled (RCD bit = 0 in Mode Page 08h, byte 2, bit 0. See SCSI Interface Product Manual, part