Appendix B
Track
Formatting
CYLINDER SKEWING
Cylinder skewing is also used on ProDrive to minimize latency time during sequential accessing
of
data.
However, instead
of
minimizing latency time due to head switching, as with track skewing, cylinder
skewing is used to minimize latency time due to a single-cylinder seek. The next logical sector
of
data
which crosses a cylinder boundary is positioned on the drive such that after a single-cylinder seek
is.
perfonned, and the drive is ready to continue accessing data, the sector to be accessed is positioned directly
under the read/write head. Therefore, the cylinder skew takes place between the last sector
of
data on the last
head at a cylinder and the first sector
of
data on the first head at the next cylinder. Figure B-2 provides an
example
of
cylinder skewing. Since single-cylinder seek times are defined on the drive, the sector addresses
can be optimally positioned across cylinder boundaries to minimize the latency time which results when a
seek has to be perfonned.
I
Cyl1
I
Head
0
_541551561571581591
FIGURE B-2 Example
Of
A IS-Sector Cylinder Skew
B·2
Appendix B Track Formatting
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