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Hard Drives


When shopping for a hard drive, you will often see terms such as revolutions per minute (RPM), seek time, and SATA™. These are ratings and technologies that dictate important aspects of the drive, like performance, compatibility, and more. By understanding what these terms mean, you can use them as metrics to compare hard drives.

Interface/Connection Type

Interface or connection type refers to the type of data connector used to attach the hard drive to the computer. It has a major impact on drive performance and compatibility.


Short for Serial ATA, it is a common standard for many types of internal data storage devices. Drives that use SATA connectors include optical drives, solid state drives, and hard disk drives. There have been three major revisions for SATA, with each improving upon speed and other factors. The last major update, SATA revision 3.0, has a maximum data transfer rate of 600 MBps.

External SATA (eSATA™)

eSATA is a variant of SATA that is adapted to the needs of external data storage devices. External SATA boasts sturdier connectors, longer cables, and more stringent power requirements. It has data transfer rates equivalent to SATA.

Universal Serial Bus (USB™)

A very common connection type for external hard disk drives. There have been several major revisions of USB, with USB 3.0 being the latest and fastest. USB 3.0 has a theoretical maximum data transfer rate of five gigabits per second.

Small Computer System Interface (SCSI)

The latest iterations of SCSI are Serial Attached SCSI (SAS) and SCSI Ultra. SAS is a common enterprise hard drive connector and features a maximum data transfer rate of six Gbps. SCSI Ultra is less common and has a maximum data transfer rate of 320 Mbps.

IEEE 1394 (FireWire®)

A type of connector that is found on some external hard drives and is an alternative to USB and eSATA. The most recent version is FireWire 800, which features a maximum data rate of 800 Mbps.


Used by network attached storage (NAS) drives to connect to a network. A gigabit Ethernet connection has a maximum data throughput of one gigabit per second.

Form Factor

There are two main form factors for internal hard disk drives, 2.5 inch and 3.5 inch. Smaller 2.5 inch hard drives can be used by both laptop and desktop computers, but 3.5 inch hard drives are too large for laptops. If you plan to use a 2.5 inch hard drive or solid state drive with a desktop, you might need a 2.5 inch to 3.5 inch adapter bracket.


A small amount of random access memory (RAM) used to hold data that has been recently read or written. Data is stored on the cache or buffer because retrieving data from the cache is quicker than retrieving data from the hard disk. A larger cache allows for more data to be stored for quick access and better hard drive performance.

Some motherboards feature technology that allows you to use a solid state drive as a cache. So instead of the typical 32 to 64 MB cache of a hard drive, you can have a cache that measures in GB. Two such technologies are Intel® Smart Response Technology and Marvell® HyperDuo.

Seek Time

Defined as the time it takes for a hard drive’s mechanical arm to reach the data’s location on the platter. Measured in milliseconds, it is only one part of the total time it takes to read data.

Mean Time between Failures (MTBF)

An estimate for the reliability of computer hardware based on testing and provided by the manufacturer. It can be used to compare reliability between multiple hard drives.

Redundant Array of Independent Disks (RAID)

It is a method of organizing several hard drives into one logical unit. With a RAID setup, you can choose to either mirror data across all drives to reduce the likelihood of losing data, or separate data across all drives to improve read and write performance.

Spindle Speed

Measured in revolutions per minute (RPM), it is used to gauge overall speed of the drive. A higher RPM allows a drive to read and write data quicker. Two common speeds for desktop and laptop hard drives are 5,400 RPM and 7,200 RPM, while high-end and enterprise hard drives can have speeds of 10,000 RPM or 15,000 RPM.

Self-Monitoring, Analysis, and Reporting Technology (S.M.A.R.T.)

It is a feature that allows a hard drive to monitor errors and anticipate failure. The information can be accessed by the motherboard, operating system, and certain applications. Users that want to see their hard drive S.M.A.R.T. report can use monitoring tools to get information such as error rate, throughput performance, average seek time performance, and more.

By NeweggBusiness Staff