PC drives and external storage drives spin and have an RPM.

I have some questions that I am struggling to find answers for and since some of you guys knew where I could find a Dwemer Puzzle Box I figured some of you may know this.

1. Where does the disc start storing information (i.e. the outer portion of the disc or the inner portion of the disc)?

2. Where is the RPM measured from (i.e. does is it measured from the outer circumference, the inner circumference or somewhere in the middle)?

3. Depending on the answer to Question 1... does this mean that drives get faster or slower as they spin (since it takes more time to travel the outer circumference than it does the inner circumference)?

Hopefully someone here is smart enough to know the answer.

Thanks in advance.

Az

It's a disc, you won't get any different RPM (revolutions per minute) readings between outer and inner parts.

1. Data starts at the inside of the disc.
2. The disc spins at different RPM depending upon where data is being read - the disc needs to go slower (less RPM) when on the outer edges of the disc so the laser can read at a constant rate.

That's my understanding of optical drives; with the magnetic type the RPM is constant and the linear velocity varies depending on the head position. I'm not sure which the OP is asking about, or if it's both. I'm also reminded that I need to brush up on filesystems and their organisation (because things like that are interesting!) but I'm rather out of date at present.

3. Depends on the track location !!!

The data rate is higher on the outer tracks (more data sectors per rotation) and lower as you go to the inner tracks (fewer data sectors per rotation)

Also if am not mistaken HDDs using the CAV method, so the disc spins at a fixed rate. This means that sectors at the outside of the disc pass under the head much faster than those at the centre.

On the other hand CDs and DVDs have a single spiral track and are (CLV) discs. Those drives change the speed at which the disc spins, so that the amount of disc surface that passes through the laser unit is constant.

This is possibly the best question I have ever read. Thank you for giving me a chuckle