Selecting Hard Drive Storage
Apple gives you some hard drive choices when you buy a Mac. The drives vary in capacity, and with some models, you have a choice of rotational speed. You can also replace the hard drive in an existing Mac with a bigger or faster drive.
You may also want to look at two other options for expanded capacity outside the Mac: NAS (network attached storage) and SAN (storage area network), which, despite the acronyms, aren’t opposites. I discuss both later in this section.
Rotational speed is a measure of hard drive speed in revolutions per minute (rpm), the speed at which the platters inside the drive spin. The faster the rotational speed, the faster the drive performance.
The lowest rotational speed you’ll find in a Mac that supports Mountain Lion is 5,400 rpm, which Apple used in some Mac mini and MacBook models. A speed of 5,400 rpm isn’t particularly speedy for a server, so consider replacing such a drive with the next level up, 7,200 rpm. This is the fastest drive you’ll see in notebooks and many desktop computers, aside from a solid-state drive. 7,200 rpm is also the standard in the high-end Mac Pro.
Apple used to offer 15,000-rpm hard drives for the Mac Pro and Xserve. In some models, Apple now offers solid-state drives, which are faster than even 15,000-rpm hard drives. Solid-state drives have no moving parts, like USB flash drives. Solid-state drives are also significantly more expensive per gigabyte than hard drives.