Here's some raw data on DEC hard drives... This will need to be more html-ized in the near future. Also more data is needed :) 

Drive    Size   FormFactor   Height  Interface
-----    ----   ----------   ------  ---------
RZ23     104MB     3.5"        1"    SCSI1 CCS
RZ26       1GB     3.5"        1"    Fast SCSI2
RZ55     320MB     5.25"       FH    SCSI1 CCS
RZ56     640MB     5.25"       FH    SCSI1 CCS
RZ58    1380MB     5.25"                       cyl=2114 acyl=2 pcyl=2112 head=15 nsect=85 rpm=5400 bpt=44823 fmt_time=4