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There are three factors which complicate data layout on
a disk. [RW94]
- 1.
- zoning To maximize storage capacity, adjacent
disk cylinders are grouped into zones. Zones near the outer
edge have more sectors per track than zones near the inner
edge. The outer zones have higher data transfer rates.
[RW94]
- 2.
- track skewing Sector zero on each track is
skewed by just the right amount to handle worst case
head or track switching times. Each zone has its own skew
factors. [RW94]
- 3.
- sparing Also called slipping or forwarding,
this is the process by which references to bad sectors are
remapped to other spare locations on the disk. In one
technique a bad sector or track is remapped elsewhere.
A more complicated technique, called slip sparing or
slipping, is to shift all of the sectors after the bad sector
by one sector or track. [RW94] [SG94]
Sparing complicates disk optimization since the good sector
may or may not be near the bad sector. [SG94]
Barnett Hsu
1998-10-31