[Simh] Mounting simh disk files in Linux

[Timothe Litt]

You're right about ODS-1, I mis-remembered that:
> he logical block containing the home block is the 
> first good block on the volume out of the sequence 1, 256, 
> 512, 768, 1024, 1280, .... 256*n.
ODS-2:

The home block search delta is computed from the geometry of 
the volume such that# if the volume is viewed as a three di- 
mensional space# the search sequence will travel approxi- 
mately down the body diagonal of the space. Since volume 
failures tend to occurr across one dimension# this minimizes 
the chance of a single failure dest-rovi ng ' bot h home blocks 
of the volume. The search delta is eomouted from the volume 
geometry, expressed in sectors# tracks (surfaces)# and cyl- 
inders# according to the following rules# to handle the 
cases where one or two dimensions of the volume have a size 
of 1, 





In most cases# the home block is located on L8N 1, 

The question, and what I'm working on, related to ODS-2
 

On 03-Mar-16 11:25, Johnny Billquist wrote:
> 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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