

So why do some solid-state drives look like 2.5-inch hard drives?

I’ll start by answering my own question. The Intel X25-M (and its 1.8-inch sibling, the X18-M) looks like an internal hard drive so that it can fit into existing laptop hard drive slots.

That strikes me as being shortsighted, though maybe I’m just ahead of the curve. It’s just that the form factor seems to lack creativity.

Before I dive into what I mean, let’s consider SSDs versus rotating storage.

There’s no question that solid-state drives are a hot topic these days. After all, who wouldn’t like fast storage that’s persistent, noise-free, and uses relatively little power? How about people who think about price/performance ratios?

Those spiffy new Intel 80GB SSDs will cost over $600. It’s true that semiconductors are on a steep process technology path, but NAND flash is already on pretty high density manufacturing processes, with 40mm coming on line currently.

MLC (multi-level cells) alleviate the capacity issue somewhat; Intel’s mainstream (as opposed to server) SSDs use a 2 bit-per-cell MLC technology to achieve higher densities. There’s technology on the books to move to 3-bpc and 4-bpc MLC levels, though what impact this would have on performance isn’t known yet.

Even given increases in chip capacity, it’s going to be many, many years before NAND storage approaches the cost per bit of rotating magnetic storage. That’s one reason Intel and other SSD manufacturers are pushing the power issue.

SSDs consume less power and generate far less heat than higher speed hard drives. Multiply that by hundreds of computers, and the power savings from both the drives themselves and the less strain on the HVAC systems is pretty significant.

SSDs are also more durable, though mobile hard drives have become increasingly shock resistant over generations. Still, there’s something to be said for being able to drop your SSD and have it keep on ticking. The problem with this scenario, though, is that if I drop my laptop, I’m likely to end up with a cracked screen, rendering said laptop useless.

Then there’s the issue of capacity and write performance. Fast desktop drives, particularly if you run them in RAID 0, tend to be substantially faster in terms of write performance than even the fastest SSDs.

This is a boon for any application that needs to write a bunch of data continuously, such as video capture and photo editing. (Don’t think photo editing writes a lot to disk? You try editing multiple RAW images and watch your drive light do the access dance, even with 6GB of memory and a 64-bit OS.)

The performance differences narrow substantially when you start talking about mobile platforms. Even fast 2.5-inch laptops, which spin at 7,200RPM, are only on par with the latest Intel and Samsung SSDs in write performance. On the other hand, traditional hard drives for laptops have recently hit 500GB, for under $200, with capacities increasing in the future.

On the desktop front, this capacity difference is increasing. One terabyte hard drives seem almost commonplace, and Seagate has already announced 1.5TB desktop drives, and we’ll likely see 2TB drives in a year or so.

Intel X25-M and X-18M SSDs

These thoughts on capacity bring me back to my original question: Why, particularly for laptops, do SSDs look like hard drives?

What I really mean is: Why are SSDs seen as replacements for rotating magnetic storage?

As more and more people carry around their digital lives in mobile form, storage capacities seem almost constrained. Even 320GB isn’t enough for some users. Sure, you can carry around external drives, but that’s just another device to carry around.

Here’s what I’d like to see: integrated SSDs.

Imagine buying a laptop with an 80GB SSD that’s just a bunch of chips on the motherboard (plus controller, of course.) The hard drive bay is empty. As an option, you can add more storage—either another flash drive, if you wish. Better yet, how about a 500GB hard drive?

Use that 80GB, integrated SSD for primary boot, applications, and storage of critical data. Have that 500GB hard drive for data that requires large capacities—music, movies, games, photographs. Of course, you’d want to back all that precious information up, but you do that anyway, right? Right?

I’m betting laptop makers are already thinking about this. Integrated SSDs make a lot of sense. In ultramobile platforms, you could make them even thinner if you don’t have to worry about a dedicated bay for something that looks like a hard drive.

And those users of those bigger, mainstream mobile PCs can have their cake and eat it too, using the SSD for most stuff, and spinning up the hard drive only when they need it.

By the way SSDs, no matter how rugged, are no replacement for good backups. But that’s a topic for another column.