SSD Testing Methodology

When we test storage devices, the two main metrics to consider are access time and transfer rate. Simply put, access time is the time is takes the storage device to start delivering data once the request has been received, while transfer rate is how fast (megabytes per second) the data comes once the transfer operation begins. With a hard disk, data transfer cannot begin until the disk’s head servo physically moves the read/write head to the correct track, and the rotation of the disk brings the designated sector under the head. Although modern servos are very fast, in the best case you’re still looking at several milliseconds to do this, while an SSD’s access time is always under a millisecond. The disadvantage is even worse if the data isn’t all in a contiguous space on the disk, since the head will have to be repositioned on the fly, leading to more delays.

Early consumer SSDs actually had slower transfer rates than the best hard disks, although their instantaneous access times more than made up for it. The zenith of consumer hard disk performance was probably reached in 2012 with the release of the Western Digital Velociraptor 1 terabyte disk. Spinning at 10,000RPM, this disk could under ideal circumstances (i.e. a synthetic bandwidth test) reach a sequential transfer rate of over 230MB/s. Keep this figure in mind as you read this review.

SSD Testing Disclaimer

Early on in our SSD coverage, Benchmark Reviews published an article which detailed Solid State Drive Benchmark Performance Testing. The research and discussion that went into producing that article changed the way we now test SSD products. Our previous perceptions of this technology were lost on one particular difference: the wear leveling algorithm that makes data a moving target. Without conclusive linear bandwidth testing or some other method of total-capacity testing, our previous performance results were rough estimates at best.

Our test results were obtained after each SSD had been prepared using DISKPART or Sanitary Erase tools. As a word of caution, applications such as these offer immediate but temporary restoration of original ‘pristine’ performance levels. In our tests, we discovered that the maximum performance results (charted) would decay as subsequent tests were performed. SSDs attached to TRIM enabled Operating Systems will benefit from continuously refreshed performance, whereas older O/S’s will require a garbage collection (GC) tool to avoid ‘dirty NAND’ performance degradation.

It’s critically important to understand that no software for the Microsoft Windows platform can accurately measure SSD performance in a comparable fashion. Synthetic benchmark tools such as ATTO Disk Benchmark and Iometer are helpful indicators, but should not be considered the ultimate determining factor. That factor should be measured in actual user experience of real-world applications. Benchmark Reviews includes both bandwidth benchmarks and application speed tests to present a conclusive measurement of product performance.

Test System

• Motherboard: MSI Z170A GAMING M7 Socket LGA 1151
• Processor: 4.0 GHz Intel Core i7-6700K Skylake CPU
• System Memory: 16GB DDR4 2133MHz
• Operating System: Microsoft Windows 10 Pro

Storage Hardware Tested

The following storage hardware has been used in our benchmark performance testing, and may be included in portions of this article:

• Crucial RealSSD-C300 CTFDDAC256MAG-1G1 256GB SATA 6Gb/s MLC SSD
• Crucial m4 CT256M4SSD2 256GB SATA 6Gb/s MLC SSD
• Crucial M550 Solid State Drive515GBCT512M550SSD1
• Crucial MX100 Solid State Drive 512GBCT512MX100SSD1
• Crucial BX100 Solid State Drive 500GB CT500BX100SSD1
• Intel SSD 311 Series Larson Creek SSDSA2VP020G2E
• Intel SSD 320 Series MLC Solid State Drive SSDSA2CW160G3
• Intel SSD 335 Series Solid State Drive SSDSC2CT240A4K5
• Intel SSD 520 Series MLC Solid State Drive SSDSC2CW240A3
• OCZ Agility 2 OCZSSD2-2AGTE120G 120GB MLC SSD
• OCZ Agility 3 AGT3-25SAT3-240G 240GB MLC SSD
• OCZ Vertex 2 OCZSSD2-2VTXE120G 120GB MLC SSD
• OCZ Vertex 3 VTX3-25SAT3-240G 240GB MLC SSD
• OCZ Vertex 3.20 MLC SSD VTX3-25SAT3-240G.20 MLC SSD
• OCZ Vertex 4 VTX4-25SAT3-256G MLC SSD
• OCZ Vertex 450 VTX450-25SAT3-256G MLC SSD
• OCZ Vertex 460VTX460-25SAT3-240G MLC SSD
• OCZ Octane OCT1-25SAT3-512G MLC SSD
• OCZ Vector VTR1-25SAT3-256G MLC SSD
• OCZ Vector 150VTR150-25SAT3-240G MLC SSD
• Patriot Torqx 2 PT2128GS25SSDR 128GB MLC SSD
• WD SiliconEdge-Blue SSC-D0256SC-2100 256GB MLC SSD

Test Tools

• AS SSD Benchmark 1.6.4067.34354: Multi-purpose speed and operational performance test
• ATTO Disk Benchmark 2.46: Spot-tests static file size chunks for basic I/O bandwidth
• CrystalDiskMark 3.0.1a by Crystal Dew World: Sequential speed benchmark spot-tests various file size chunks
• Iometer 1.1.0 (built 08-Nov-2010) by Intel Corporation: Tests IOPS performance and I/O response time
• Finalwire AIDA64: Disk Benchmark component tests linear read and write bandwidth speeds
• Futuremark PCMark Vantage: HDD Benchmark Suite tests real-world drive performance

Test Results Disclaimer

This article utilizes benchmark software tools to produce operational IOPS performance and bandwidth speed results. Each test was conducted in a specific fashion, and repeated for all products. These test results are not comparable to any other benchmark application, neither on this website or another, regardless of similar IOPS or MB/s terminology in the scores. The test results in this project are only intended to be compared to the other test results conducted in identical fashion for this article.

Note: Our existing library of SSD test results is almost entirely based on internal SSD drives, connected to a SATA 6G port or an m.2 port. The Transcend ESD400 is a portable drive that connects over USB 3.0, and this will be at a performance disadvantage compared to SATA: the raw data transfer rate is slower (5gbs as opposed to 6gbs), and SATA/AHCI support additional performance optimizations not available to USB drives. Although modern external USB drives are far faster than earlier generation internal SSDs, they will never be as fast as the equivalent generation internal SSDs.