On 03-Mar-16 11:12, Johnny Billquist wrote: > What does the physical disk geometry have to do with Files-11? > At least ODS-1 couldn't care less. > > Johnny The home block search sequence - for both ODS1 and ODS2 - uses the geometry to determine where the HOM blocks are located.
Usually block 1 is the primary HOM block. But the spec requires a backup HOM block, and the search sequence varies based on the geometry. It was an attempt to search in 3 dimensions to avoid probable media damage scenarios. Think of each attempt as a rotation, move inward and up. But there are special cases. Read the spec for details. If a reader insists on finding the second (or subsequent) HOM block, it can't without the geometry. The geometry is also (sometimes) used for file placement, which a reader shouldn't care about.
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