Shopping for single platter hard drives

Recently, when I needed to upgrade an internal 3.5 inch hard drive on an old computer, I shopped for the drive with Defensive Computing in mind.

Like many, I started with what was on sale at my favorite retailer and ended up considering a couple drives in the Seagate Barracuda 7200.12 series. How to chose between them? Of course, capacity, price and speed all come into play, but I was looking at something else too. Something not in the specs offered at the retailers website.

The number of platters.

Internally hard drives are spinning round discs. Some have a single disc, some have two, some have three. Multiple discs are stacked on top of each other like LP records used to be on turntables.

Most people couldn't care less about the internal physical makeup of a hard drive. But I do. I want the fewest possible platters, preferably just one. Fewer platters make the drive mechanically simpler and thus less likely to fail, long term.

You can think of a disc platter as being an entry in the mechanical failure lottery. This is a lottery you don't want to win, thus the fewer entries the better.

Laptop users get an additional benefit, fewer platters should need less power, thus extending battery life.

Determining the number of platters, however, takes detective work.  

In my case, I dug up the detailed specs for all the drives in the Barracuda 7200.12 line in the Data Sheet PDF at Seagate's website.

The line consists of six different drives ranging in capacity from 160GB up to 1TB. To snoop out the fewest platters, I looked at the specs.

First off is weight. Drives with more platters are bound to weigh more. The drives in the 7200.12 line come in two different weights, 1.4 and 1.2 pounds. The two highest capacity models, 1TB and 750GB, are the heaviest.

Next is the height. Drives with fewer platters can be shorter than those with multiple platters. In the 7200.12 line the drives come in two heights 1.02 inches and .78 inches. The two highest capacity models are the tallest. 

Then there is the average operating power. This also segregates the two high capacity models from the rest of the line. They need more power, further indicating they have more platters.

It seems pretty clear that the 500GB, 320GB, 250GB and 160GB models have fewer platters than the 750GB and 1TB models. My hope is that they have a single platter.

The 500GB and 320GB models include a 16MB cache, the lowest capacity models have an 8MB cache. On the hope that more cache means fewer disk I/Os, my first choice would be either the 320GB or the 500GB model.

Now, which one was on sale again?

Update: October 27, 2009. According to a Seagate spokesperson, "non-operating shock is the impact resistance of the drive when it is powered down (not spinning) and its head is parked. Operating shock is the shock resistance of a spinning drive."

All the drives have the same operating shock resistance. The four lower capacity models have a higher non-operating shock resistance than the two higher capacity models.