2.5 vs. 3.5 Hard Drive

By Jason Artman

While shopping for a new hard drive, you may have seen the terms "2.5 inch" and "3.5 inch" and wondered what they meant. The two terms describe different form factors that hard drives can be manufactured in, and the two types are not necessarily interchangeable. Depending on what you plan to use your hard drive for, however, you may have the option of using either type. Learning how these hard drive types differ can help you make the right choice for your application.

The Basics

Generally speaking, 3.5 inch hard drives are made for desktop computers, while 2.5 inch drives, as denoted by their smaller size, are meant for laptops. A 3.5 inch hard drive will not fit into a laptop, making a 2.5 inch hard drive your only upgrade choice in this case. However, desktop computers have more internal space, giving you the option of choosing either.

3.5 Hard Drive Benefits

Speed, capacity, price and convenience are the primary reasons for choosing a 3.5 inch hard drive over a 2.5 inch one. The highest capacity 3.5 inch hard drives hold a massive 2,000 GB of data and are very easy for even computer novices to install. For most modern hard drives, it is only necessary to tighten a few screws and connect two cables. Your computer will handle the rest. The fastest 3.5 inch hard drives can read data at more than 131 MB/sec. With 3.5 inch hard drives, all of this speed and capacity comes at a very small cost; a 2,000 GB drive can be purchased for just $200.

2.5 Hard Drive Benefits

The primary reason for installing a 2.5 inch hard drive in a desktop computer is the extremely low level of noise produced by the quietest 2.5 inch drives: 19 to 21 decibels at a distance of one meter, as opposed to the 21 to 23 decibels produced by the average 3.5 inch drive. In a computer specifically constructed for silent use, such as one that might be utilized in a home recording studio, 2 to 3 decibels can make a world of difference. For most other desktop computers, though, a 3.5 inch drive would be preferable. The 2.5 inch hard drives cannot compete in terms of speed or price, being able to read data at a maximum of about 101 MB/sec and costing $150 for 750 GB.

2.5 Hard Drive Installation

A 2.5 inch hard drive cannot be installed directly into a desktop computer. The chassis of the computer will not have drive bays to accommodate it. However, this problem can be resolved by an inexpensive adapter such as the Upgradeware HD25-S, costing about $10. The HD25-S allows you to install a 2.5 inch hard drive into a desktop computer's expansion card slot.

Solid State Disks

So far, this article has only discussed conventional hard drives with rotating magnetic platters. However, a new type of hard drive called a Solid State Disk (SSD) is quickly becoming more popular. SSDs utilize flash memory, rather than magnetic media, and are able to transfer data at amazing speeds (the fastest SSDs can read data at more than 230 MB/sec). Also, since SSDs have no moving parts, they are completely silent. Unfortunately, they are also costly. The fastest SSDs, manufactured by Intel, cost more than $350 for just 32 GB of storage.