

Ask HN: Multi-head disc drive - cool-RR

Hello everyone,<p>Does anyone know why we use disc drives that have only one reading/writing head? 
This applies to any optical disc, regardless if it's CD or DVD or Blu-Ray or whatever.
Why don't they put two or three heads in each drive, so we could burn a DVD in 2 minutes? Also, I find it annoying that it takes like 10 seconds from the time you put a disc in the drive to when the computer reads it.<p>Maybe something like this exists and I just never heard of it? Does anyone have an idea?
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cperciva
This has been attempted; my understanding is that IBM had a hard drive where
each platter had independently controlled heads about 20 years ago.

It turned out to not work very well. Disk heads have to seek very accurately,
and stay unmoving very accurately once they fine the right location; having
other disk heads moving around made this incredibly difficult.

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russell
There have been multi-headed drives is the past when seek times were in the
hundreds of miliseconds. It's not done now because it greatly increases cost
and the complexity of the software, and doesn't work very well. A dual-headed
drive would probably cost more than two single headed drives.

