HDD - Which numbers really matter???


Feb 8, 2011
Ok guys,

I am just starting my second build, and something Iv never really looked into before was the numbers associated with HDDs. The only one I really paid any attention to previously was the Spindle speed, making sure my HDD was 7200rpm rather than 5400rpm (my first build was a while back).

What I want to know is, do the numbers mean much at the end of the day? Or is a HDD a HDD regardless? So the big questions are.....

Do the brand names matter? Is a Seagate Barracuda better than a WD Raptor? or are they much and such?

Does Spindle Speed matter, I know that 7200 is the norm, but Iv read that 10,000 and 15,000 are not worth the extra money, is this true??

Buffer Size - Dont know a thing about this, is it important to get a 64mb rather than a 32mb?

Seek Time?? as above, ie is it important?

External Transfer Rate - Obviously important if your transferring data from 1 drive to another, but will a higher speed mean that any programs installed on that drive will load/run faster??

Any help advice appreaciated. My plan is 2 run with at least 2 (or maybe even 3) HDDs, 1 for Windows and programs (lower capacity), the other (1TB) for Data. Any links to what would best suit my needs would be appreciated too



Higher rpms give you better rotational latency and generally the faster they spin the better the performance. Average seek time and sustained data transfer rates are the more important values to look at.

Consider a reasonable size SSD (120gb range) for your OS and programs, they just crush rotating drives. Use good 7200rpm HDDs for your data.
also google the model of drive your looking at. some drives have longer warranty under the same brand. also some drives have higher failure rate then others. few years ago seagate had the better drives but some people here on the forum will say the getting a high failure rate with there retail drives. some says black label of wd right now has the lowest failure rate.


Nov 12, 2010
Here's a lowdown on the things you should care about.

1. Spindle speed. You were right to prioritize this above other specs. The speed the platters rotate determines the amount of time it takes for the hard drive to get to the data you want read. This is by a very wide margin the largest contributor to latency in an HDD.

2. IOPS. You won't see this listed on many HDDs, but it's the number of Input/output Operations Per Second. This is the number of reads your drive can handle in a certain period of time. Higher is better, as it means your computer needs a higher load to bog it down.

3. Transfer speed. This is less important than you'd expect, because you only get the rated transfer speed when all the data is sequential (in one long section of the disk) so you don't have to seek to a new part of the disk repeatedly. This kind of read operation is very rare in the real world.

The advantage in IOPS is what makes SSDs so good. A good HDD can put up decent throughput, especially 10k and 15k RPM drives, but they can't compete at all in IOPS, and as a result get bogged down much more easily. An SSD can handle many tens of thousands of IOPS, while a mechanical drives rarely break 10k.

I really wouldn't recommend a 10k RPM drive for a home computer, though, and 15k drives require special SAS controllers. You won't notice a huge improvement over a good 7200 RPM drive, and they cost quite a bit more. If you're going to spend big on storage, get an SSD or hybrid drive.


Apr 25, 2012
Yep, a basic setup these days should include #1 SSD for OS and programs, #2 HDD for data, #3 external HDD for backup. Always have a backup in place... most people learn this the hard way.