As a data recovery company, our data recovery experts get to see a lot of drives on a daily basis, and there are hundreds of models out there. Here are a couple of key aspects that help categorize drives.

One obvious factor is the physical size of the drive. While other sizes exist, we are typically seeing desktop drives (3.5”) and laptop drives (2.5’”). Desktop drives can currently hold up to 2TB in capacity, while laptop drives have just reached the 1TB barrier.

The second big aspect is whether it is an internal or an external hard drive. A lot of people don’t realize that an external hard drive is in fact just a housing, a case for an internal hard drive, equipped with interfaces like USB or FireWire to be able to connect the drive to a computer externally.

Here it is important to know that the makers of external drives are not necessarily the makers of the actual drive mechanism inside. What this means is that unless you’re buying an external drive from one of the big drive manufacturers (i.e. Hitachi, Samsung, Seagate, or Western Digital), the actual hard drive inside is not actually from the maker of the case (e.g. LaCie, SimpleTech or G-Data to name but a few), but typically from one of the big four mentioned above.

This is important in a harddrive recovery scenario, as the problem is in most cases not with the enclosure, but with the drive mechanism inside. As such, if a problematic external drive comes to us, we will have to remove it from the enclosure, in order to be able to test the actual hard drive. Unfortunately, most external drives made by the drives manufacturers themselves nowadays come in cases that cannot be opened without leaving marks or even rendering them useless after opening.

Finally, the last major point of distinction that needs to be mentioned is the interface used by the drives. For the last few years, basically all new drives shipped with the SATA (serial ATA) connector. If a drive is older than that, chances are it is still sporting the PATA (parallel ATA, also known as IDE) connector. While the SATA connector is the same on both 2.5” and 3.5” drives, laptop drives carry a smaller variant of the IDE connector compared to their desktop cousins, which means an adapter may be necessary to connect them internally to a desktop computer.

If you have an empty enclosure or want to replace a drive in an enclosure you own, it is therefore important to know which interface the case supports, as it will only support one of the two. If your case supports the IDE interface but you buy a SATA drive, you will not be able to mount the drive in your case and will have to get a different case (one that supports SATA) instead, and vice versa.