Seagate heeft in het verleden een scsi schijf, ik geloof een barracuda, geproduceerd met twee setjes heads. ze zijn echter maar even in de handel geweest want het was te duur om te produceren en het was interessanter om gewoon 2 schijven te kopen.
ik heb er een stukje over gevonden:
Seagate Barracuda 2HP
This Seagate drive, long out of production now, used an almost unique approach to high performance. Although similar in most respects to the then-current range of high-speed Barracuda drives, it used two heads in parallel to double data transfer rates.
Almost all hard drives have more than one read-write head; four and six-head drives are common, and a dozen or more is not unusual. But only one head is used at any one time, and the maximum data transfer rate is governed by the amount of data passing under the head. The Barracuda 2HP, however, was able to split the data stream up into two halves, sending one half to each of two heads, and recombine the data when reading it back. In an era when the best 7200 RPM drives were capable of 50 or 60 Mbit/second transfer rates, the Barracuda 2HP managed 113Mbit/second. It was easily the fastest hard drive on the planet.
This was not a new idea, but it was the first, and so far the only implementation of it in a mainstream drive. Imprimis (Control Data's storage division, now part of Seagate) had produced a series of multiple-head parallel drives for supercomputers starting as early as 1987.
So why has 2HP technology disappeared now?
First, it's possible to achieve the same results by combining several individual drives in a RAID array, letting the RAID controller card or controller software perform the complex task of splitting and recombining data. RAID has become dramatically cheaper over the past few years, and is commonplace in high-end server systems.
Secondly, time to market. New drive models are coming onto the market more and more rapidly. By the time a design team has taken an existing high-speed drive and spent a lot of money developing a twin-head parallel version of it, the next generation of single-head drives are nearly ready - and they will equal the performance of the 2HP drive at much lower cost simply through increased spin rates and ever-higher areal density.
In short, 2HP drives will not have another chance to become cost and performance competitive unless there is a slow-down in areal density increases - currently running at 60 percent a year. Until then, the Barracuda 2HP will remain one of a kind.