Just how important is it to have more than one disk?

Question

I'm confused about this.  I've seen that, in some cases, having only one disk may be fine, even though it's reading and writing from/to the same disk.  However, I've read countless times that it's very hard, with the music conductor analogy that I've seen several times, that it's not good at doing both at once.  If I were to simply use two disks in regards to one (let's not go into the specifics of each disk), what speeds and where would be increased since reading and writing all to the same disk is no longer as much of an issue?

Answer 1

If I were to simply use two disks in regards to one (let's not go into the specifics of each disk), what speeds and where would be increased since reading and writing all to the same disk is no longer as much of an issue?
Compare it to moving from one house to another. A lot of stuff needs to be moved (you will be surprised how much stuff you have acquired in the course of years) from A to B.
Steps to be taken are:
Load the car or van with your stuff.
Drive from A to B.
Unload the stuff at B.
Reverse from B to A.
This continues until you have moved all your stuff to the new house.
While the basic steps remain the same, if you had two cars, the move would be done in half the time. If you had three cars at your disposal, the move would be done in a third of the time and so on.
A single car can only use D or R at a single moment in time. It can't do both at the same time. Once you put the gear in D, you can drive forward. If you want to reverse, you have to stop the car, first put it in N and then in R to reverse. The same with SATA disks. They can read data, have to stop, and then write, then stop and then read again.
The more cars (read disks) you have at your disposal, the quicker the move from A to B is accomplished. The faster each car (disk) is, the quicker. Of course this requires some planning. It is no use to have all cars waiting in line to load the stuff at A and none unloading at B at that same moment. It also makes no sense to spend time loading a huge couch or chest into the smallest car available, when it could be loaded easily into the big car or van that is waiting next in line. Just load only small stuff into the small car, like silverware or porcelain and let the big stuff to the big car(s). Think file type allocation.
There is not much you can do about rush hour traffic jams, apart from planning the move outside rush hour. Think 'tuning'.