History (1991): Two Independent Heads Per Platter on HDD

In the 5.25-inch form factor, but with five 3.5-inch platters, Conner Peripherals has developed a mechanism that was only on IBM’s large disks, reminds Jim Porter (Disk/Trend).

Usually, a drive has only one actuator, this time the manufacturer integrates two actuators that work independently in the same unit.

The thin-film recording head on each actuator reads and writes data independently of the other. Each data path contains an independent channel, buffer controller and sequencer. This means it is possible at the same time to read and write data on the same disk, to read or write 2 blocks of data in 2 places simultaneously.

The Chinook CP-5500 with 510MB formatted, a SCSI-2 interface, available for $1,595 for an evaluation unit, is considered by Bill Schroeder, VP of Conner, as a “miniature disk array.”

“Virtual” performances announced with this process are outstanding: the effective seek time and the rotational latency is cut in half (3ms seek time and an average latency of 6.7ms), 9,000rpm (2×4,500) and especially 140IO/s, which means this unit aims applications that need frequent and random accesses.

Chinook accepts up to 32 concurrent requests for data. This queue depth allows the drive to make use of sophisticated ordering algorithms to decrease mechanical latency.

This new device mostly aims, for the time being, a reduced number of customers with precise needs, and it’s the first time that the US manufacturer puts out a product that is not for the mass market.

According to Conner Peripherals, the Chinook drive was developed in conjunction with several major OEM computer manufacturers who are expected to announce their system in the coming months.

This article is an abstract of news published on the former paper version of Computer Data Storage Newsletter on issue ≠46, published on November 1991.

Note: This drive was finally a flop but a similar idea was recently released by Seagate.