Will there ever be 20,000 RPM HDDs?

Sometimes making a projection from past trends gives you the wrong answer.

Number series play their part in this deception because we can sometimes see a pattern in numbers which falsely predicts what will come next.

Here's an example:- 1, 2, 4, 6, ...what comes next?

There are many ways you can continue this series.

And you may be thinking - "8".

But that's not my answer.

The example I had in mind was the historic development of the horse drawn stage-coach. And the series of numbers - 1, 2, 4, 6, .. is the number of horses which pulled your carraige.

As people became wealthier and demanded more comfort in their road transport - a "coach and 6" became a luxurious form of high speed travel which gave its name to many English pubs. As we know from our current vantage point - high speed road travel did not advance to the "coach and 12" but instead took a detour via the internal combustion engine and the motor car.

Here's another example:- 3,000, 4,200, 5,400, 7,200, 10,000, 15,000, ??

Most of you will easily recognise that adding the addendum "RPM - Revolutions Per Minute" to this sequence charts the increase in hard disk drive rotation speeds during the past 20 years.

Where is this going?

Well you may be sorely tempted to add a number like 20,000 to the end of this sequence. That would be a not unreasonable assumption. And I might have been tempted to do the same myself but a number of signals have steered me in a different direction.

A white paper by Fujitsu Trends in Enterprise Hard Disk Drives contains this observation "Ultrahigh-speed HDDs rotating at speeds exceeding 20 000 rpm have also been researched but not commercialized due to heat generation, power consumption, noise, vibration and other problems in characteristics, and a lack of long term reliability." (See also Squeak! - Green Storage )

Independent market research suggests that high end servers will standardise on on the 2.5 inch (and smaller) form factor - because this is easier to deploy in blade servers and high density server farms. And a recent report by IDC said that the fastest growing segment in the high end server market was servers from Sun which pack in more processors per U(nit) of rack space than competitors - and at a lower wattage per server than other vendors.

Combining these trends together suggests that what customers of big multi user servers would really like is faster disk drives - with lower power consumption. But that's just not possible with hard disk technology.

Enter the solid state disk. SSDs in the same form factor as 15K RPM hard drives are available in the same capacity and typically offer faster throughput and hundreds of times faster random IOPs - which is a better measure of how disk speed translates to server speed in most multi-user systems. (The exceptions are storage servers which have been optimised to deliver streaming video - in which the performance gap is much smaller.) The SSDs also use less power and are more reliable.


Nevertheless it is a truth universally acknowledged that a 146GB 15K RPM drive from Seagate today costs an order of magnitude less than a similar form factor (but faster) SATA SSD with similar capacity from vendors listed in our Solid State Disks Buyers Guide.

That's where Microsoft's Vista and the new generation of hybrid flash-hard drives give us the vital clue about what is going to happen next.

True - this technology was originally designed for notebooks. But if the OS can recognize a solid state disk and cache frequently used files to the flash part of it - then migrating this clever OS to a server version is not a very big step. And fast SSDs are already available.

Now - whether the hard disk oems get around to designing high speed bybrid disks - or whether systems integrators find a quick and dirty solution - such as stuffing 1 SSD for every 4 HDDs in the same box first remains to be seen.

The latter - SSD cached HDD hybrid array solution - works in a server rack environment - and makes hybrid server disks extinct before they even appear in a Powerpoint product marketing plan. Sorry guys.

But here's a warning. If you do ever see a 20K RPM hard disk appear in a press release or catalog then give it a wide berth - unless you work for a computer museum. That's not the way the market will go.