Western Digital Working On a 20,000 RPM Drive

MrKaos writes "Western Digital seems to be preparing for the onslaught of solid-state drives set to impact its market by developing a 20,000 rpm hard drive. Similar to the VelociRaptor line of drives, the new drives are speculated to be offering lower capacity as a tradeoff for faster seek and write times." This report out of Taipei is the only word on the rumored WD 20K drive. It's said to be a 2.5" drive in a 3.5" enclosure, for efficiency of cooling — the arrangement the Register enjoyed poking fun at when the 10K drive was upgraded last month.

Seagate responds

We've taken the next step by mounting our 15,000 rpm drives in an external enclosure which then spins the drive at a further 10,000 rpms, for a total system speed of 25,000 rpms. Initial benchmarks are very promising!

Re:Seagate responds

Before now, nobody understood why I have all of my computers sitting on top of turntables. Now I'll just point them to your post, since they couldn't fathom what I meant when I said it makes it run faster.

I had also tried mounting them in a paint can shaker to get at least another 15Hz out of the CPU, but I couldn't stand the noise.

Re:Seagate responds

Come on get your science right.

You don't get +5 Funny for "getting your science right".

immovable object?

I wonder if these really fast hard disks will have to be kept stationary. More specifically: I wonder if conservation of angular momentum (manifested, for example, in gyroscopic precession) becomes a real issue if any torques were put on a spinning disk.

Re:immovable object?

The smaller diameter / mass will tend to reduce bad effects from conservation of angular momentum.

Re:immovable object?

Even though they are intended to be used in server hardware where they are going to be kept stationary you will also be able to find users that are going to use them in their home computers or in servers that are on the move.

This means that the gyro effects are worth to consider. Also considering my experience from WD disks I'm not sure that I would want to use them for anything reliable.

For a solution where speed is important but the data itself can be re-created or of less critical value they can be OK.

Solid State

I'm wondering why they are still going in this direction, as hard drives are the slowest part of a computer. Why hasn't a solid state / flash ram approach taken over? Is it feasible to have a hybrid solid state/mechanical solution?

Re:Solid State

Economics.

Is there a point to this?

Is there still really a point to huge RPMs? As data density increases, speed should increase naturally. Move over the same distance at the same speed on a drive with twice the density should mean that one has read twice the data in the same amount of time -- therefore reading speed is twice as fast, right? This should even work on low-capacity drives by simply using small, high-data-density disks.

Re:Is there a point to this?

No, not right, that's assuming that the writes are being done sequentially. Hard disks are random access devices, and while they can definitely do sequential reads and writes, and quite a bit faster, as soon as the files are not next to each other or are fragmented you're going to lose that advantage.

Re:Is there a point to this?

The higher speed drives aren't so much for their sequential transfer rates by themselves, but their random seek rates. They are trying to get high I/O per second rates (IOPS), which is what a lot of servers need to be at their peak.

Re:Is there a point to this?

You can't just wave a magic wand and double the density. Many of these things are interrelated in a complex manner. Increased density requires new head designs, new and improved electronics, new coatings for the platters, etc.

Re:Is there a point to this?

In other words, this speed increase could enable the drive to do 10% more random I/Os per second.

We at the NSA are interested in things which are more random, and would like to subscribe to your newsletter.

Add heads?

It seems strange to continuously up the rotation speed, adding noise, vibration, heat and shortening the life of the drive. Why not just add another set of heads on the opposite side of the drive? You get many of the same benefits - increased sustained transfer rate, but also reduce the seek and latency. To maintain the form factor, reduce the size of the platters (use 2.5" drive platters in a 3.5" drive).

Re:Add heads?

Good idea. I for one would prefer to go solid state.

Re:Add heads?

I had this same idea, actually, only I thought to have 4 sets of heads, rather than just two.

I also thought of arranging what would essentially be two 2.5" disks in a 3.5" enclosure. These could either act as a stripe for faster, higher capacity data storage, or as mirrors of each other, providing redundancy at the cost of speed and capacity. If the drives in your RAID stripe are mirroring themselves, you needn't worry about mirroring your RAID stripe, no?

Re:Add heads?

I'd go even further... use the old 5 1/4 "half height" form factor, stack 8 platters in it, with 4 sets of heads, spin it at 5400 rpm to keep the power requirements down to reasonable.
This would give you 8 platters * 2 sides * 400 Gbit/in^2 [wikipedia.org] * 50 in^2 (estimated working area surface area per platter) ==> 40 Terabytes in a single package, with an average access time on the order of 5 millisecond, and a sustainable transfer rate of at least 300 Megabytes/Second.
Even without the 4 sets of heads, that would still be a 40 Terabyte drive!

As far as RAID goes, it's just one drive, it's all or nothing, so don't think it would count as it's own mirror.

--Mike--

Re:Add heads?

Modern hard drives can only read from one head at a time. The tracks are packed in such that thanks to uneven thermal expansion, only one track will be lined up under a head at any given time. But two sets of heads might work as gp suggested.

Re:Add heads?

It's been done before, iirc, but they tend to be more expensive, and the multiple heads run the risk of creating unintended harmonics. Most of the time it would be cheaper and faster to use two drives with one set of heads, than one drive with two sets of heads.

Re:Add heads?

Well, that would add to the number of components that could fail, and require a high speed bus between the two controllers, as well as a shared cache and all the headaches that would bring with it (think SMP caches being ping-ponged). Then you've got to sync your interface to the system bus as well as the new internal buses. On the other hand, you can just crank the knob up to 11 and go 20K RPMs on known, tried and true, technology.

Re:Add heads?

Connor actually did this right around the time 3.5" drives started.

http://en.wikipedia.org/wiki/Conner_Peripherals#Performance_issues_and_the_.22Chinook.22_dual-actuator_drive [wikipedia.org]

It could read from either set of heads, but I believe could only write from one set. Writes can be posted in a write-behind buffer, so this didn't impact performance.

Western Digital? Oh good!

Now it can lose my data twice as fast the last one I bought.

Re:Western Digital? Oh good!

Bad luck? I've never had a problem with WD, I swear by 'em. One of us is having unusual luck, and I'd prefer to think it's you. ;)

Maxtor, on the other hand... I lost count of how damned many Maxtor drives I've seen die. Single most failure-prone drive manufacturer I've come across. Everyone else, I see a dead drive here and there, nothing serious, but Maxtor is obscene.

More Parallelism

the new drives are speculated to be offering lower capacity as a tradeoff for faster seek and write times

How about if they make drives with very thin platters, but stack them up into individually addressable bit slices of the bytes they store? Then the time to read a single bit from the rotating media could read an entire byte, reassembled in the logic.

Or if the platters can't be that thin, how about sacrificing some storage capacity for say 2x2 platters, which could give 4x parallelism.

That parallel access might stave off competition from solid state drives for a couple extra years.

Re:They should work on a 20,001 RPM drive

20001: A Speed Odyssey.

Sorry, couldn't resist.