Benchmark your data storage device

When you buy a data storage, or build your own, say, a RAID, you naturally want it to work fast. I have never met a single person who does like the slow drives.

However, often the real-life read/write speed of a device is somewhat different from the values advertised by a vendor or in case of DIY device from the design-time speed estimation.

There are many reasons why a device performs slower than expected. For example, when analyzing NAS performance, you should take into account the throughput of network to which you connect the NAS. For the external drives connected to a PC via USB, the overall performance will be limited by USB bus which at least five times slower than the slowest hard drive.

However, before you set to find out why your data storage device doesn’t provide the maximum performance, let’s learn how to measure the performance.

The process of measuring various performance characteristics of a data storage device is called benchmarking. The main measured parameters are:

  • linear read and write speed - speed at which a device can read or write sequential blocks of data;
  • access time - time for which a device spits out the first block of the requested data;
  • Input/Output operations Per Second (IOPS) - a number of read or write operations a device handles per second…

Typically, linear read/write speed and access time are represented in charts with maximum and minimum values highlighted; IOPS is usually just a number.

It is very easy to analyze these characteristics - fast device is a device with a maximum linear speed and IOPS, and a minimum access time.

How to benchmark a data storage device

  1. Download and install any hard drive benchmark software. Typically, you can always find a free one.
  2. Launch the tool and select a device for benchmarking. Typically, you can test both physical disks and partitions.
  3. Wait until the tool finishes measuring the performance parameters. It usually takes about five minutes.
  4. Analyze the output data.

If you deal with a regular hard drive (or a partition on it), you should get something like this:

Linear read speed decreases smoothly with a maximum value of about 100-120 MB/sec and a minimum of 50-70 MB/sec. Disk access time is a bell-shaped curve with a maximum around 10-16 ms. A regular hard drive produces about 50-100 IOPS.

For a solid state drive (SSD) you get a somewhat different picture. Linear read speed just fluctuates between 100 and 300 MB/sec, while access time is about 0.1-0.3 ms. IOPS value for an SSD is measured in thousands, typically upwards of 4000 IOPS.

If what you measured differs significantly from the above average values, it means either that something wrong with the device or your system, at least storage part of it, is not set up properly. In this case you should find the reason for the reduced performance.

Another interesting point is that you can benchmark storage devices before using them in the system. Then you can choose the optimum placement of data to get the most out of your PC. Typically, the operating system and frequently-used software and data are stored on the fastest storage, while the bulk of rarely-used data is stored on the slower storage, maybe even on the server over the network.


About the author -Elena Pakhomova is the Marketing and Development for data recovery software company