An Explanation of Read and Write Speeds

Read/write speeds differ between solid state drives and hard drives

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Read/write speeds are measures of performance on storage devices. Tests can be performed on internal and external hard disk drives, solid-state drives, storage area networks, and USB flash drives.

When checking the read speed, you're determining how long it takes to open (read) something from the device. The write speed is the opposite — how long it takes to save (write) something to the device.

How to Test Read/Write Speeds

CrystalDiskMark is one freeware program for Windows that tests the read and write speed of internal and external drives. You choose a custom size between 500 MB and 32 GB, whether to use random data or just zeros, the drive to test and the number of passes that should be performed, with more than one providing more realistic results.

ATTO Disk Benchmark and HD Tune are a couple of other free benchmark tools that can check a drive's read and write speed.

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 MB (megabytes) of data every second.

If you need to convert MB to KB or some other unit, you can enter the equation into Google like this example: 15.8 MBps to KBps.

SSD vs. HDD

Solid state drives have the fastest read and write speeds, outpacing hard disk drives. Here are a few of the fastest SSDs and their read and write scores:

Samsung 850 Pro

  • Available Capacities: 128 GB to 1 TB
  • Interface: SATA III 6 Gbps
  • 550 MB per second read (256 GB)
  • 520 MB per second write (256 GB)

SanDisk Extreme Pro

  • Available Capacities: 240 GB to 960 GB
  • Interface: SATA 3 to 6 Gbps
  • 550 MB per second read
  • 520 MB per second write

Mushkin Striker

  • Available Capacities: 240 GB to 960 GB
  • 565 MB per second read
  • 550 MB per second write

Corsair Neutron XT

  • Available Capacities: 240 GB to 960 GB
  • 560 MB per second read
  • 540 MB per second write

Hard disk drives were first introduced by IBM in 1956. An HDD uses magnetism to store data on a rotating platter. A read/write head floats above the spinning platter reading and writing data. The faster the platter spins, the faster an HDD can perform.

HDDs are slower than SDDs, with an average read speed of 128 MB per second and a write speed of 120 MB per second. However, while HDDs are slower, they are cheaper. The cost for hard drive storage is about $.03 per gigabyte versus an average $.20 per gigabyte for SSDs.