Disks, Spin No More

In mid-January, Taiwan-based Power Quotient International (PQI) announced that it had created a 2.5" (laptop size) hard disk. At 64GB, this disk might not initially seem very interesting, until you notice its most interesting aspect: It's a solid state disk (SSD), available with either serial ATA (SATA) or parallel ATA (PATA) interfaces.

Yes, you read that correctly, there are no moving parts.

Imagine this scenario: Your flight hits an air pocket while your system is writing a large file to disk. Both you and that hard disk experience a 3g drop. Miraculously, only your tailbone and your heart rate are affected. You've had no data loss, and no head crashes. PQI claims the disk can take 1000 gs, and that seems sufficient to me; I doubt any laptop could survive a 1000g event, and I'm sure I couldn't.

It's not all good news, though. (It never is.) The price might just give you pause. I couldn't find a price for the 64GB model, but several sites were offering PQI's 32GB disk for $1800. That's painful, particularly given that a standard rotating hard disk of that size would cost less than a tenth of the price.

And what about performance? My current laptop runs with Seagate's fast and capacious 160GB perpendicular drive. That drive offers an average seek time of 12.5 milliseconds. Because the PQI drive lacks a mechanical head and actuator arm, it has a seek time of essentially 0 milliseconds, so the mechanical disk is clocked on that score. But seek is just the time required to find the data. Once that data is found, how long does it take to shovel it off the drive and onto the IDE interface? Well, according to the drive's documentation, the Seagate can pull data off of its platters at the rate of up to 44MBps. The solid-state PQI drive takes a bit longer, at 25MBps for a read and 18MBps for a write—a bit slower, but in the rotating disk's ballpark.

If I were to swap my 160GB rotating disk for a 64GB SSD, my wallet would be a bit lighter and my data accessed a mite slower, but I'd be able to compute longer. Whereas the 160GB disk uses 2 watts for a read operation and 1.8 watts for a write operation, the SSD consumes a mere 0.12 watts for a read and a hair less for a write.

Clearly, I won't be "going silicon" for my hard disk needs any time soon, unless I win the lottery and choose to store less data on my laptop. However, I wonder how much longer it will be before we can say goodbye to what often seems the least reliable part of a system: the rotating hard disk.

In the 25 years since the PC debuted, we've slowly seen most of the low-reliability components fade away. The 5.25" floppy disk was troublesome and used heads that needed frequent cleaning and occasional alignment. Daisy wheel printers were noisy and prone to jamming, and dot-matrix printer heads suffered their own kinds of alignment problems and deafened their owners. Today's laser and ink-jet printers still suffer the problems endemic to anything that has to grab paper and shuffle it along, but maintenance has become quite simple—mostly because changing a cartridge changes most of the printer's moving parts. In another example of bygone PC pains, 10BaseT Ethernet networks, which one employee could bring down by merely improperly disconnecting his PC, are just a bad memory.

But hard disks just won't go away. The idea of entrusting our data to small devices that read and write data with disk heads that fly above their platters on a cushion of air more narrow than the width of a human hair—heads that often fly at speeds exceeding most highway's speed limits—has always given me the shakes. But until someone figures out how to pack those bits onto non-volatile RAM chips more cheaply, we'll all have to keep living by the same motto we've lived by for decades: "Back up early … and back up often!"

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