While configuring CKD storage on a new IBM DS8880 I discovered that the default 
number of cylinders for a 3390-27 and a 3390-54 has changed.
Caution should be taken when your defining new storage.

I've always assumed that a 3390-27 had 32,760 cylinders.  Not the case anymore, 
if using the GUI and the DISK or Mod1 calculations.  You end up getting 30,051 
cylinders.
I've also assumed that a 3390-54 had 65,520 cylinders.  Now the default number 
of cylinders is 60,102.

These new calculations are now divisible evenly by 1113, a 3390 Mod-1

If you have a need to define these two volumes sizes please keep this in mind 
as this could cause serious issues when trying to migrate from the older volume 
sizes to the newer sizes.
I did find the new smaller sizes documented in the DS8870 & DS8880 Architecture 
and Implementation Redbooks.

Ken Mazer

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