McGuire_Ed@GRINNELL.MAILNET.UUCP (07/16/86)
Chris, I came across an archived note you sent in April '86 regarding BACKUP efficiency. In part: >BACKUP efficiency is sensitive to a number of factors. Tape block >size is one of the more important ones; the following suggests the >largest (and most efficient) blocks for each density: > 800 bpi 8192 ( 8Kb) bytes/block (default) > 1600 bpi 16384 (16Kb) bytes/block > 6250 bpi 65024 (63.5Kb) bytes/block. >The larger the tape blocks, the fewer I/Os are required, and the >faster things will happen. I believe TU80s are streaming drives, so >it may also help to specify the maximum 5 buffers. (Note that 5*63.5K >equals 635 memory pages for buffers alone, so allow a large working >set.) I must be missing something. Why not use the maximum block size permitted by BACKUP no matter what the density? Are these architectural limits imposed by the recording method? McGuire_Ed%GRINNELL.MAILNET@MULTICS.MIT.EDU (MIT-MULTICS.ARPA)