Physical Dimensions; Seek Time; Read Look-Ahead And Caching - Seagate MEDALIST 1080SL Product Manual

Medalist 1080sl SCSI Product Manual, August 1995

1.4 Physical dimensions

Height (max)
Width (max)
Depth (max)
Weight (max)

1.5 Seek time

All seek time measurements are taken under nominal conditions of
temperature and voltage with the drive mounted horizontally. In the
following table:
Track-to-track seek time is the average of all possible single-track
seeks in both directions.
Average/typical seek time is a true statistical random average of at
least 5,000 measurements of seeks in both directions between ran-
dom cylinders, less overhead.
Full-stroke seek time is one-half the time needed to seek from logical
block address zero (LBA 0) to the maximum LBA and back to LBA 0.
Track-to-track
Average/typical
2
seek time
seek time typ
4.5 msec read 12.5 msec read
3.5 msec write 15.5 msec write
Note. Host overhead varies between systems and cannot be specified.
Drive internal overhead is measured by issuing a no-motion seek.
Drive overhead is typically less than 1.0 msec.

1.5.1 Read look-ahead and caching

The drive uses algorithms that improve seek performance by storing data
in a buffer and processing it at a more convenient time. Three methods
are used: read look-ahead, read caching and write caching. These are
described in Appendix C.6.
2. All possible one track seeks are divided into the time required to perform those seeks.
Only the mechanism time is used; interface overhead is excluded.
3. All possible seeks are divided into the time required to perform those seeks. Only the
mechanism time is used; interface overhead is excluded.
4. The average of 1000 full stroke seeks is used in this computation. Only the mechanism
time is used; interface overhead is excluded.
0.748 inches (19 mm)
4.00 inches (102.1 mm)
5.00 inches (127.0 mm)
0.75 lb (340.2 g)
Full-stroke
3 4
seek time typ
25.0 msec read
27.0 msec write
5
Average
latency
5.6 msec