I remember (many) years ago seeing an IBM mainframe storage drum. It had a few platters, each with 4 heads every 90 degrees, and each heads was the width of th

I remember (many) years ago seeing an IBM mainframe storage drum. It had a few platters, each with 4 heads every 90 degrees, and each heads was the width of the platter. The fixed heads had one read/write head over each track. sort of brutally effective. EDIT: found it. IBM 2305 fixed head storage module: https://ed-thelen.org/comp-hist/IBM-ProdAnn/2305.pdf https://ed-thelen.org/comp-hist/IBM-ProdAnn/2305.pdf https://bitsavers.org/pdf/ibm/2835/GA26-1589-5_2835_2305_Reference_Oct83.pdf https://bitsavers.org/pdf/ibm/2835/GA26-1589-5_2835_2305_Ref... poking around looking for this, it seems that lots of early IBM disk drives had multiple heads. They would have some conventional heads, and a few fixed heads over tracks with frequently accessed data.