29 December 2017

Spinning Wheel [update]

It's deja vu all over again. Anandtech reports on a "new" Seagate HDD with heads split between two arm sets. The comments don't think much of the idea. Nor do I. If only because it's a lousy implementation of an ancient innovation. My lower brain stem memory told me that mainframe DASD routinely had multiple arm sets, way back when.

So, off to the innterTubes for some documentation. A few minutes found this paper, from 2008.
A later work [45] explored the possibility of having multiple arms that are capable of moving independently, and the IBM 3380, which was a 4-actuator drive released in 1980 for the IBM System/370, embodied this feature.
[this is the note: [45] A. J. Smith. On the effectiveness of buffered and multiple arm disks. In Proceedings of the
International Symposium Computer architecture (ISCA), pages 242-248, 1978.]

It's not unimportant that the IBM mainframes use CKD storage protocol at the time such drives were in use (now emulated on hard-formated PC HDD).

And, here's the Godzilla of HDD. I knew there was such a beast. With CKD, head per track has lots o benefit.
Read/write heads were fixed in position over each track. That eliminated seek time and contributed substantially to system performance. Data could be written at rates up to 3 million bytes per second.

That rate was in 1970.

No comments: