  Smaller disk cluster factors? 
 The Question is:
 
VMS 7.2 changes the restrictions on minimum cluster size on Files-11 volumes
to allow more efficent use of new larger disks. It would appear from reading
Kirby McCoy's book on Files 11 that ODS2 has been capable of supporting this
all along. My question i
s: Can earlier versions of OpenVMS properly process a Files-11 volume
created on OpenVMS 7.2? If not, what changes have been made to ODS2, and how
do you protect earlier versions from accessing these volumes.
 
 
 The Answer is:
 
  OpenVMS has not been able to deal with smaller cluster factors, the
  particular change around support for creating and accessing the larger
  storage bitmap is new in the OpenVMS V7.2 release.
 
  Disks with these newer smaller cluster factors are emphatically
  not compatible with earlier OpenVMS releases, can not and should
  not be mounted on releases prior to OpenVMS V7.2.  (The OpenVMS
  documentation should be very clear on this requirement.)
 
  Default operations, disk initialization and such will continue to
  create volumes with cluster factors compatible with earlier OpenVMS
  versions.  Only if the cluster factor settings are explicitly
  overridden will the new (smaller) cluster factors be available.
 
  There is/was no software mechanism available to lock out access to
  these newer big-bitmap volumes on earlier OpenVMS releases, short of
  changing the volume structure code and rendering the volume entirely
  inaccessable by earlier versions.  This change would have required
  changes elsewhere in the V7.2 file system and utilities to correctly
  enable, configure, detect and process this new volume format code,
  and was thus this option was not considered feasible for inclusion
  in the release.  Thus the current clearly documented dependence on
  the "if it hurts, don't do that" solution, and the use of appropriate
  and compatible default values for the cluster factor.
 
