On 2016-03-03 17:21, Timothe Litt wrote:
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.
I should check, but I'm pretty sure the home block copies for ODS-1 is
at 256, 512, 1024... Logical block number. So not based on geometry at all.
But let me check later tonight, to be sure...
Johnny
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