Why do hard disks/CD’s have to spin fast


Can we write the data as a single track, that way they could spin very slowly, like a vinly record.


In: 1

The language of a hard disk is binary. It’s only 0’s and 1’s. Every single process your computer goes through ultimately comes down to a 0 or a 1. You need a bajillion 0’s and 1’s to make whatever you’re doing, so it needs to run super fast to get through all of that data in a timely manner. You could make one that spins really slow, but you wouldn’t be able to put much data on it.

The encoding of data has a minimum physical size it can be and still be reliably decoded. CDs and HDDs are what you get when you balance reliability and read speed.

First of all, the speed of spinning equal to the speed of reading data. Slow spinning – less data per millisecond.

As to the single track – what happens when you delete a 1MB file from that track, but need to write a 2MB file instead? There is not enough space in that part of the track where the 1MB file used to be.

People have no patience.

When they click “next song” or “open file”, they want immediate response. If the disk spun at 60RPM it would take as much as a whole second before the device/computer responded. That’s unacceptable, so the disks need to spin faster, about 500 to 1000 times faster for computers and 10 times faster for a CD.

Let’s take the most recent 20TB HDDs as an exemple. They are made of 9 platters, each of which can be written on both sides, so 18 surfaces to write to.

That means 21,990,232,555,520 Bytes, or 175,921,860,444,160 Bits.

Each side of a platter is then about 9,773,436,691,342 Bits.

Each of these Bits have to be written, that’s a whole lot of them, it has to spin fast to write all of that quickly.