Disk/Tape Request Size Questions

[Judah Greenblatt]

> What limits exist on the size of single transfers
> to/from disk and tape (tape block size) in the Unix
> world, and elsewhere.

The maximum tape block size for Unix machines I have used:
AT&T 3B20	6K max,  5632 byte recommended
Pyramid 98x 	30K max
CCI Power 6/32	32K max, 16K recommended

> What effects on performance are there for using larger
> size transfers (i.e. do other requests pay a penalty
> while a large transfer is being serviced)?

On the CCI, transfers of over 16K bytes at 6250 BPI disable interrupts
overly long, causing the system to loose clock interrupts.
-- 
Judah Greenblatt		"Backward into the Future!"
Bell Communications Research	uucp: {bellcore,infopro,ihnp4}!whuxcc!judah
Morristown, New Jersey, USA	arpa: whuxcc!judah at mouton.com
  * Opinions expressed are my own, and not those of the management.