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 used to 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. Read/write speed tests can be performed on internal and external hard disk drives as well as storage area networks and USB flash drives.

Highway lights at night
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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 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. For example: 15.8 MBps to KBps.

How to Test Read and Write Speeds

CrystalDiskMark is a freeware program for Windows that tests the read/write speeds of internal and external drives. You can 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. You can also 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 can check a drive's read and write speeds. The former works for both operating systems.

SSD vs. HDD Read/Writes Speeds

Before buying a new hard drive, you should know the difference between SSDs and HDDs. A hard disk drive (HDD) use 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 can perform. Typical read/write speeds for an HDD top out at 200 MBps.

Instead of a disk, solid-state drives (SSDs) use semiconductors to store data, which is much more efficient. Consequently, SSDs have 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, can deliver read/write speeds above 500 MBps.

While HDDs are slower than SDDs, they are also cheaper. The cost for hard drive storage is about $.03 per gigabyte versus an average $.12 per gigabyte for SSDs, but prices are steadily falling.

How Fast Is Fast Enough?

For most users, 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.