Solid state storage

I still have a hard time referring to the new crop of mass storage devices as “flash drives.” The “flash” part is correct, seeing as they’re built with flash memory, but the “drive” part is just … wrong. There aren’t any moving parts. It’s like referring to “dialing” a telephone. Or the telephone “ringing.” You don’t hear that good ol’ Ma Bell … bell … anymore.

In any case, solid state storage has come a very long way in the two years since I last talked about it.  You no longer have to build your own device from parts cobbled together.  Today you can get flash “drives” in the 2.5″ form factor with capacities up to 512 gigabytes.  That’s right, half a terabyte of solid state storage.  Granted, the 512 GB units are ridiculously expensive, but the 128 GB units are pretty reasonable.  We just got one in the office for about $300, delivered.  That’s expensive compared to conventional storage ($2.35 per gigabyte compared to 10 cents per gigabyte), but it’s still an incredible deal.  It’s less than you would have paid for a 128 gigabyte hard drive five years ago.

The new crop of solid state storage devices really is worth taking a look at.  The one we got (G.Skill Falcon), claims throughput of 230 MB/sec on read and 190 MB/sec on write.  In initial tests, we were able to sustain very close to the 230 MB/sec read rate, and our sustained write rate was close to 150 MB/sec.  That’s about three times as fast as we can read a conventional hard drive, and four times as fast as we can write.  We won’t be replacing all of our hard drives with these units, but we certainly can use the speed in a couple of critical I/O-bound applications.

Earlier generations of these solid state storage devices had some interesting limitations.  The first generation units were almost universally slower than or, at best, just a little faster than conventional hard drives.  Many of them also used more power than a spinning hard drive.  And some were just unreliable.  Things have improved quite a bit.  Hard drive manufacturers have gotten power consumption down to the 6 or 7 watts range, but that’s still 50% more than the 4 watts or so that the SSDs are taking.

The cost per gigabyte is huge and even a 200% performance increase doesn’t justify that price for the normal user.  But imagine you’re a developer with a laptop computer that has the typical slow laptop hard drive.  A lot of my development tools are I/O bound on my laptop.  Just try starting up Visual Studio some time.  Tripling the I/O throughput could very well greatly improve the development experience on that machine.  That would be $300 well spent.

There are other advantages of SSDs besides the performance boost, but again they won’t justify the cost increase for the average user.  The reduced power consumption mentioned above is less of a benefit than you might think because the hard drive takes relatively little power when compared to the CPU, RAM, and display.  Still, any little bit helps by reducing generated heat and increasing battery life.  Shock resistance and temperature tolerance are much higher on the SSDs, and since there are no moving parts the thing is absolutely silent.  It seems that the lack of moving parts would make the thing more reliable, too, but it’s hard to say.  I don’t know if I can believe the 500,000 hour (57  year) MTBF that hard drive manufacturers claim, much less the 1.5 million hours claimed by the SSDs.

One of my coworkers pointed out that the SSD or something similar is essential to private pilots who are flying unpressurized aircraft over 10,000 feet.  Modern avionics packages often include computers that display moving maps and download real time weather data.  That data has to be stored somewhere, and a conventional hard drive becomes unreliable at high altitude because  there isn’t enough air to float the head over the platter.  Considering what avionics packages cost, an additional $300 for an SSD wouldn’t even be noticed.

I wouldn’t recommend the SSDs for normal users, simply because of the high cost per gigabyte.  But if you need a relatively inexpensive way to increase your I/O throughput, if your computer has to run in areas that are outside a conventional hard drive’s operating environment, or if you just want to have the latest geeky toy, then by all means pick one of these up.