On Fri, Feb 01, 2013 at 12:03:32PM +1000, Warren Toomey wrote:
> The 6th Edition update to the CACM paper says:
> 
> 	Our PDP-11 has a 1M byte fixed-head disk, used for file system
> 	storage and swapping, four moving-head disk drives which each
> 	provide 2.5M bytes on removable disk cartridges, and a single
> 	moving-head disk drive which uses removable 40M byte disk packs.
> 
> The 7th Edition update says:
> 
> 	Our own PDP-11 has two 200-Mb moving-head disks for file system
> 	storage and swapping.

And Dennis' paper on the Evolution of Unix says:

	During the last half of 1971, we supported three typists from
	the Patent department, who spent the day busily typing, editing,
	and formatting patent applications, and meanwhile tried to carry
	on our own work. Unix has a reputation for supplying interesting
	services on modest hardware, and this period may mark a high
	point in the benefit/equipment ratio; on a machine with no memory
	protection and a single .5 MB disk, every test of a new program
	required care and boldness, because it could easily crash the
	system, and every few hours’ work by the typists meant pushing
	out more information onto DECtape, because of the very small disk.

Any guesses as to the hardware?

0.5MB: RF11-A/RS11
1.0MB: RS04/EJS04
2.5MB: RK05/RK11-D
40MB:  RP03/RP11-C
200MB: My peripherals handbooks only go up to 1975.

Cheers,
	Warren