Hard drive specs and speed....

I’m shopping for a hard drive, and I would like to understand why two drives that seem to be identical, from the same manufacturer, would be priced differently, as well as what to look for to assure the best speed.

The specs refer to:

buffer: which is faster, bigger, smaller? (8mg vs. 32 mg)
transfer rate I understand, and RPM speed.

What else is there?

For instance, a bunch of Western Digital drives are all SATA internal 300 MBps, 1 TB, 3.5", yada. The only differences are buffer size that I can see, but the prices don’t follow the buffer size, and the range of prices is $30 from low to high. And yes, all at one seller.

So…what gives?

And at the end of the day, what do I want to be sure about in order to get the best speed?

Do you have the specific details on the drives you are researching? It’s often easier to make comparisons if one has details. Have you visited the Western Digital site and used their compatibility charts? Or maybe compare side by site at TigerDirect or Newegg?

Yes, that’s why I came here to ask. They all list all the different aspects of the drives, they just don’t explain what they mean.


There are three things that affect the performance of a modern disk drive.

For the first two, you kinda have to know how a hard drive works. The OP probably understands most of this already, but for the benefit of others reading this thread I’ll explain it. The disk drive has disks in it which spin. Over top of the disk you have a “head” which reads from or writes to the disk. The data is arranged like rings on a tree. To access the data, the drive first has to move the head over the correct “ring”. Then the head can read or write the data as the disk platter spins underneath it.

So, the first two things that affect performance is (1) how quickly you can get the head into position, and (2) how fast the platter spins under the head. The first one is called the track to track seek time. This is a time measurement, so the lower the number the better. The second is the RPM of the drive. Faster (higher RPM number) is better.

Back in the old days, that’s all you really needed to know, but modern drives cache data. If you read track 7 sector 1, then track 7 sector 2, then track 7 sector 3, it’s a good bet that track 7 sector 4 is coming next. Modern disk drives are smart enough to know this, and recognize certain other patterns as well, so what they do is they go ahead and read in track 7 sector 4 before you even bother to ask for it. This way the data is already in the drive’s cache memory when the computer comes along and asks for it, and then the computer doesn’t have to wait for the drive head to move and the data to be read from the platter. Generally speaking, the more caching you do, the better performance you’ll get, though this is only generally speaking. The caching algorithms used also come into play, but drive manufacturers don’t tend to publish much about that. Basically, as you are looking at specs, the more cache the better.

There are also new and refurbished drives, new pulls, or variations in OEM warranty handling.

I have seen hard drives with anything from 15 days to 5 year warranties.

The hard disk makers are also now producing separate lines for various purposes. For example, Western Digital has these lines:

  • green: environmental, low power usage, but also slightly lesser performance. Used often for notebooks, or for large arrays of drives where conserving power is important.
  • blue: their normal line for most home uses. Uses more power, but somewhat better performance than the green line.
  • black: highest performance line (also most expensive). Used where high performance is needed, and price/power use is no object.

They offer the same size drive in each of these lines, but the cost & performance vary. I think the warranty offered is also different.

I came in to say basically this. There are differences in drives that are not necessarily apparent from specs. Manufacturers will often have an “enterprise” class drive that is theoretically more robust and may have a longer warranty, a “quiet” or “green” drive that sacrifices some performance, and a general class drive. These frequently come in both OEM and retail packaging with retail costing a little more.

The drives may also be from different model years. Generally it pays to get the latest drive iteration as it has a greater chance of having tweaked firmware. On the other hand, you often can get a discount on older models. The Seagate 7200.11 series drives had been discounted quite a bit when the 7200.12 series units were released.

Nothing to do with OP question but I suggest checking out ZipZoomFly I have bought numerous hard drives from them and they always gave me excellent quality and service and if you keep checking you will hit a deal. I’ve never seen anyone beat their deals. But keep checking for them

Also, a drive may fall in price because the company released a newer one thats more appealing, and needs to make the older stuff, which is stuff available at retail outlets, appealing via price. Ive gotten crazy deals on hard drive lately because of all the new models coming out. I can get a 500gig drive for a good price because of the recent flurry of 1TB releases. Like most things in the computer world, if you wait 6-12 months, you can get a decent discount.

So if youre comparing the newest to something thats slightly older, but with the same capacity, you might find that the older design might use more power or it might have a bigger cache or something else that still makes it attractive.

I just wanted to mention SSD (solid state drives), which are much more expensive per Mb, but the good ones* can be quite a lot quicker for typical work loads than even the best magnetic disk drives.

  • Beware, SSD is fairly recent technology in the consumer market, and there are plenty of slow-as-hell-under-real-world-conditions SSDs available. Intel’s drives are somewhere at the top of line of general use drives right now. I’ve worked with a few of those and they really are amazingly fast when you’re launching some large application that uses a gazillion files when starting, like Photoshop. But an Intel X-25m at 80 Gb will cost just under 200 euros, and that price will also get you a 2 Tb - 12 times as large - Magnetic drive, if you can live with the drop in performance.