Why have all HDD the same rpm?

[IJALB]

Does anybody know why all HDD have the same rotation speed?

Of course, there are different rpm: 4200, 5400, 7200, 10000.

But why are all vendors using only these rpm's?
In many other cases, companies are using measurably features for marketing.
Why isn't there a vendor who builds a HDD with 5600 so that it would be the fastest HDD of it's class?

Is there a technical reason? I think it should be possible to build a HDD with any rpm.

[ThinkPad]

For mass production, sticking to a similar, routine template generate most profits. For example, Hitachi might have one assembly line for 5400 drives and another for 7200 drives. Say if you wanted 6000rpm, that would require a whole new assembly line which would be costly to the company, especially if it is not sold in masses. If they only made a handful of 6000rpm drives, it might cost more than current SSDs!

The reason why SSD drives are so costly is because it has not yet become a mainstream product. Once other companies develop SSD technology and mass production beings, the prices will drop.

[IJALB]

For mass production, sticking to a similar, routine template generate most profits. For example, Hitachi might have one assembly line for 5400 drives and another for 7200 drives. Say if you wanted 6000rpm, that would require a whole new assembly line which would be costly to the company, especially if it is not sold in masses. If they only made a handful of 6000rpm drives, it might cost more than current SSDs!

Of course, it's expansive to have more assembly lines in one company.
I'm not wondering about this.

However I don't know why other vendors don't make other drives. For example, Hitachi makes its drives with 5400 (and 7200) rpm and Seagate can make its drives with 6000 rpm (and 8000) rpm and so Seagate also have only two assembly lines.
Why is there no vendor using other drives than the standard drives (5400, 7200 and 10000 rpm)?

I think it could not be so expansive to built a own 6000 rpm drive and use this drive for all mainstream HDD's.

[ThinkPad]

For mass production, sticking to a similar, routine template generate most profits. For example, Hitachi might have one assembly line for 5400 drives and another for 7200 drives. Say if you wanted 6000rpm, that would require a whole new assembly line which would be costly to the company, especially if it is not sold in masses. If they only made a handful of 6000rpm drives, it might cost more than current SSDs!

Why is there no vendor using other drives than the standard drives (5400, 7200 and 10000 rpm)?

I think it could not be so expansive to built a own 6000 rpm drive and use this drive for all mainstream HDD's.

Probably because there is no demand for such drives. Create demand and they will build it (and take your money too )

[IJALB]

Probably because there is no demand for such drives. Create demand and they will build it (and take your money too )

There is often no demand for features but demand is often defined by the marketing department. For example, nobody need 12 mega pixel on a small digital camera (with a small sensor) but the marketing department need this feature. In real life it would be better to have 6 mega pixel for better pictures.
Maybe this is not a good example but if you build a drive with higher rpm it can be faster. A 6000 rpm drive could be faster than a 5400 rpm drive and it could be more silent than a 7200 rpm drive.
The same rpm for all HDD vendors is like if all car vendor would use only three kinds of engines (only 4 cylinder with 2 liter, 6 cylinder with 2.5 liter and 8 cylinder with 4 liter). But in real life the are also engines with 3 and 5 cylinders and mainly with different cylinder capacity for the same number of cylinders.

First I'm not sure if there is no demand and secondly I don't know if the HDD vendors have no marketing departments.

[RealBlackStuff]

Be glad that there is some sort of standard!
Otherwise the companies would not compete with each other who has the fastest, toughest, best, coolest etc.
Best of all, they need to compete with their price to get YOUR custom!
No chance if you have to compare apples (e.g. 7200rpm) with pears (e.g. 8000rpm)

[ThinkPad]

Probably because there is no demand for such drives. Create demand and they will build it (and take your money too )

There is often no demand for features but demand is often defined by the marketing department.

You are right. To a marketing department, more pixels is higher value, more desirable and thats what people want. There is no research and study for HDD users so its hard to put something out that people dont know about.

[IJALB]

Be glad that there is some sort of standard!
Otherwise the companies would not compete with each other who has the fastest, toughest, best, coolest etc.
Best of all, they need to compete with their price to get YOUR custom!
No chance if you have to compare apples (e.g. 7200rpm) with pears (e.g. 8000rpm)

I don't have a problem with this standard but I would also have no problem if they (the HDD vendors) wouldn't use this standard.
Standards are good an necessary in many cases but I see no need for standardized rpm's.

I also don't see a problem to compare drives with different rpm's: 4.200 und 5.400 U/min im Vergleich or 5400 rpm and 7200 rpm

Conclusion: I just wonder why ...

[Troels]

Well, no HDD drive manufacturers produce there own motors - it's licensed to JVC, Nidec, NMB etc.
What you get are motors with some variance... they rarely spin at exactly 7,200 RPM for example.
As to why exactly the 4,200 , 5,400 and 7,200 speeds - no idea, Although i know all about modelling of DC motors, i cannot tell why these figures were chosen exactly.
Usually the RPM is limitied by the torque presented primarily as the load (the disks). Back in the days somebody probably randomly chose a motor, set a limit for acceleration time and size and thus moment of inertia of the disk so he/she could predict the current draw at spinup not to exceed a specific limit.
It's probably as stupid as why exactly a sampling rate of 44,1 kHz for CDs were chosen instead of ADAT 48 KHz for example...