An Explanation of Read and Write Speeds

Read/write speeds measure the performance of a storage device. The read speed refers to how long it takes to open a file from the device, and the write speed is how long it takes to save a file to the device. Perform read/write speed tests on internal and external hard disk drives as well as storage area networks and USB flash drives.

How Are Read and Write Speeds Measured?

Read and write speeds are typically recorded with the letters ps (per second) at the end of the measurement. For example, a device that has a write speed of 32 MBps means that it can record 32 megabytes of data every second. It's also common for speeds to be expressed in MB/s.

How to Test Read and Write Speeds

CrystalDiskMark—a freeware program for Windows—tests the read/write speeds of internal and external drives. Select a custom file size between 500 MB to 32 GB and choose whether to use random data or just zeros to run the test. Set the number of passes that should be performed.

Blackmagic Disk Speed Test is a similar tool for Macs. ATTO Disk Benchmark and HD Tune are a couple of other free benchmark tools that check a drive's read and write speeds. The former works for both operating systems.

SSD versus HDD Read/Write Speeds

Before you buy a new hard drive, research the difference between SSDs and HDDs. A hard disk drive uses magnetism to store data on a rotating disk. A read/write head floats above the spinning disk reading and writing data. The faster the disk spins, the faster an HDD performs. Typical read/write speeds for an HDD top out at 200 MBps.

Instead of a disk, solid-state drives use semiconductors to store data, which is much more efficient. Consequently, SSDs clock faster read and write speeds than HDDs. They are also more durable since they don't contain as many moving parts, so SSDs are more likely to survive being dropped. The fastest SSDs on the market, such as the Samsung 860 EVO, deliver read/write speeds above 500 MBps.

While HDDs are slower than SDDs, they are also cheaper. However, pricing for SSDs is steadily falling.

How Fast Is Fast Enough?

For most people, read/write speeds aren't a huge concern unless you regularly work with large files. For businesses, time is money, so spending a little more on a faster drive might be worth the investment.