PDP-11 disk image question

On 2/20/19 1:25 PM, Glen Slick via cctalk wrote: Paul K's explanation and Glen's example matches my own experience in this area. I don't have a CMD controller, but I move images between SIMH and both Emulex UC07 and Dilog SQ706A MSCP/SCSI Controllers. I've used RT11, XXDP, RSX11M+ and VAX VMS on both physical hard drives and SCSI2SD emulated disks. The physical SCSI drives I use have SCSI reassign capability. This allows the controller/drive to manage media defects.? This is transparent to any of the OS'es. The controller presents the disk simply as a continuous logical disk of disk blocks and the geometry has no effect. ?? Space reserved for bad block replacement is not visible to the OS. I make sure the number of logical blocks is maintained exactly as I move the images back and forth between SIMH and physical Machines. The disk type RA90, RA81, etc never makes a difference.? The MSCP controllers read the media size directly and report the disk logical capacity to VMS Drivers. If I move an VMS ODS-2 SIMH disk image to a larger SCSI disk drive then problems will occur.? For ODS type volumes, my understanding is that bitmap.sys file won't have room to manage the extra space.?? I also try to avoid edge cases for disk sizing that involve powers of two - e.g. 2**32.?? In my general experience, I have found boundary check problems in different situations (especially non-Digital). Disk NASTY$DKA100:, device type DEC RA92, is online, mounted, file-oriented ??? device, shareable, error logging is enabled. ??? Error count??????????????????? 0??? Operations completed?????????????? 2653 ??? Owner process???????????????? ""??? Owner UIC????????????????????? [SYSTEM] ??? Owner process ID??????? 00000000??? Dev Prot S:RWPL,O:RWPL,G:R,W ??? Reference count?????????????? 48??? Default buffer size???????????????? 512 ??? Total blocks???????????? 7603200??? Sectors per track??????????????????? 63 ??? Total cylinders????????????? 474??? Tracks per cylinder???????????????? 255 ??? Volume label????????? "VAXVMS73"??? Relative volume number??????????????? 0 ??? Cluster size?????????????????? 9??? Transaction count?????????????????? 155 ??? Free blocks????????????? 3072564??? Maximum files allowed??????????? 419336 ??? Extend quantity??????????????? 5??? Mount count?????????????????????????? 1 ??? Mount status????????????? System??? Cache name "_NASTY$DKA100:XQPCACHE" ??? Extent cache size???????????? 64??? Maximum blocks in extent cache?? 307256 ??? File ID cache size??????????? 64??? Blocks currently in extent cache 307161 ??? Quota cache size?????????????? 0??? Maximum buffers in FCP cache??????? 557 ??? Volume owner UIC??????? [SYSTEM]??? Vol Prot S:RWCD,O:RWCD,G:RWCD,W:RWCD ? Volume Status:? ODS-2, subject to mount verification, protected subsystems ????? enabled, file high-water marking, write-through caching enabled. I don't see a discrepancy on SCSI2SD V5 cards between configuration size and VMS reported block,? The size used is recorded on the SCSI2SD V5 card.? The SCSI2SD V6 adapters store the drive configuration on the last block of the microSD and I believe reported capacity is reduced by 1. ? Perhaps the CMD is doing similar to allow the media to be interchanged between controllers. ? Jerry