Can several magnetic heads in a cylinder of one disk read or write simultaneously?

lastans7

12/16/23, 5:24 PM

For example, a disk has 8 surfaces, each has one magnetic head. If all but one heads disappeared, the disk can reach 10MB. What will the speed if using all heads?

2 + 0

hard-drive

Score:0

Server

Zac67

12/25/23, 10:15 PM

While there may be many read/write heads in a hard drive, only one of them can be active at any time.

One reason for that is that there is only one amplification/decoding circuit. In theory you could add more, but a more subtle reason preventing that is that HDDs use embedded servo information for the linear actuator.

The embedded servo aligns the single active head to its current track. Since there's only one actuator, only that one head is aligned. It's not possible to align all heads simultaneously due to manufacturing tolerances, thermal expansion and small deviations from perfectly circular tracks.

So, regardless of the number of heads, the sequential read/write speed of a rotating disk drive is ultimately defined by its recording density and rotational speed. (Unless there really are multiple actuators like in Exos 2X drives, or you are referring to ancient drives using stepper motors or dedicated servo heads.)

+ 3

Ray Butterworth

12/26/23, 1:44 AM

[Hard Drive Technology Timeline](https://datarecovery.com/rd/history-of-hard-drive-technologies/#:~:text=1965) indicates that all the heads were used simultaneously in the old technology. (That's also how I remember it working from when I worked with disks in the 1970s.)

Zac67

12/26/23, 7:15 AM

In the 1970s and 80s with stepper technology that might have been true. But that''s more a topic for [retrocomputing.se].

Ray Butterworth

12/26/23, 1:43 PM

I wonder how long it will be before *all* moving-part-storage becomes retro.

Score:0

Server

Romeo Ninov

12/16/23, 5:50 PM

Theoretically you should get 8*10MB/s=80MB. But this is kind of abstract speed because you need to have 8 information management blocks to get info from each head (not sure but IMHO there is only one and it switch between heads). And if your information is not organized based on cylinders and fill one track you will have you heads back and forth to combine info from different areas.

+ 0

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Can several magnetic heads in a cylinder of one disk read or write simultaneously?

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.