There are several methods for identifying the best internal hard drive. In most cases, the physical size and connection type are useful for narrowing down the available options. Once you have a smaller list of drives the capacity, seek time and data transfer rate are often enough for most users. Occasionally, the size of their cache and the amount of noise they make will help make the final decision.
The first method of narrowing down an internal hard drive has very little to do with the drive itself. There are two common types of internal hard drives: IDE (integrated drive electronics) and SATA (serial advanced technology attachement). Some motherboards have room for both, but most will only accept one type of drive, so you need to find out what your motherboard can handle. Next is the physical size—a typical desktop computer needs a 3.5” drive and a laptop requires a 2.5" drive. This nearly always the case, but there is the possibility that a system is different.
Many people will buy a new internal hard drive for storage. As a result, capacity is often a very important factor for many buyers. Drive capacity is typically expressed as gigabytes (GB) and terabytes (TB). This printed size is the unformatted capacity; after formatting the drive will lose about 10% of its total space.
An internal hard drive has a quality called seek time. This is the amount of time that it takes for the drive to find stored information. This time is typically measured in milliseconds (ms), and you want that number as low as possible. Typical home drives range between 9 and 12 ms, but drives with much higher and lower seek times are available.
The data transfer rate is the speed at which the internal hard drive is able to send and receive information. Some drives give a specific transfer rate, like 3 GB/sec, while others do not. If the drive doesn’t specify a transfer rate, then the drive's spindle speed, measured in revolutions per minute (RPM), give a rough indication. The three most common RPMs are 5,400, 7,200 and 10,000 with higher being better.
The drive's cache size is a type of internal memory. This will store information that the drive feels will be needed and commands that it is currently unable to execute. Since this information is held in memory rather than recorded on the drive, it is much faster to retrieve. The larger the cache, the more information may be stored. The cache’s size is measured in megabytes (MB), and the higher the better.
The last common factor in picking a hard drive is noise. Drive noise is measured in audible decibels (dBA), and you want the number as low as possible. While this factor is often not important for many users, some systems require very quiet components.