Samsung 840 120GB SSD Review

The 120GB Samsung 840 Series SSD features the powerful 8-channel MDX controller and TLC NAND. While this value SSD comes at a very good price, it also features much lower speeds than its larger capacity brethren. We put this value SSD through our suite of steady state tests to see if it can pass muster.


Synthetic Benchmarks

ATTO Disk Benchmark

ATTO Disk Benchmark is one of the industry standard benchmarks. ATTO is used to generate many of the sequential specifications on SSD packaging and marketing statements. ATTO is a very simplistic tool that generates easy to understand results for most users.

One of the key complaints about ATTO from many of the enthusiast crowd is that it uses easily compressible data. For drives that rely upon compression (LSI SandForce controllers), this benchmark will only tell half of the story, and the rosy half of it at that. Tests with incompressible data will show much lower scores at the very same measurements with the LSI SandForce controllers. Used in conjunction with other tools that test with incompressible data, ATTO can provide a good view of overall storage subsystem performance.

ATTO serves to verify that the rated specifications on the box are in fact attainable, and that the device is in basic good working order.

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ATTO testing points out the drastically reduced write speeds of the 120GB Samsung 840. The maximum write speed comes in at 138MB/s. The read speed is impressive, weighing in at a maximum of 554MB/s.


HDTune Pro provides an in-depth look at many different aspects of storage system performance, and allows for many customizations in testing that are beyond what other benchmark programs offer. One key aspect of HDTune pro testing is that it tests over the entire surface of the drive. This eliminates 'burst' results, providing a more accurate representation of the overall sequential speed. This can reveal certain characteristics in drives which are normally overlooked.

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HDTune Pro Read results reveal that the entire line of Samsung SSDs perform well in the pure read speed category. The Intel 335 and Kingston V300, our value competitors, also score well in this test.

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HDTune Pro Write tests the sequential write speed of the SSDs, and here we can again see the drastic reduction in speed from the underlying TLC NAND. The sequential write speed is abysmal in relation to the competing offerings. For any type of write intensive workload, such as installing a program, editing pictures, or copying files, this SSD is going to take an appreciably longer amount of time to finish the task. MLC value SSDs double, and also triple, the write speed of the 120GB 840.

Access Time آ– Iometer

Iometer is a comprehensive utility that can be an intimidating testing tool for the uninitiated. One of the most relevant metrics that it can test is also the simplest, the measure of the access time of the attached storage. Latency is one of the key measurements that can relate directly to a fast, responsive computer. Latency is the measurement of how fast the device can respond to a single request, and many utilities measure access time with a number of different approaches. Unfortunately not all measure correctly, so we will test with a 4k random access at a QD of 1, which is the industry standard. We attain our numbers by testing at 4kQD1 with a 5 sec ramp time for 30 seconds. Three runs are conducted and the results are averaged. The HyperX 3K, which leverages a SandForce controller and relies upon compression for part of its performance, is tested with both random (incompressible) and repeating (compressible) data to highlight the two levels of performance.

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Average Read and Write Latency results show that the 120GB 840 seems to handle the latency aspect of read and write I/O processing down to respectable levels. When compiling the results I was pleasantly surprised by these results, until I compiled the results below.

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Maximum Read Latency takes into account the longest single read access (file) requested during the duration of the test. By measuring this "Longest I/O" it is possible to see the efficiency of the controller and firmware of the SSD. If there is a correlation between a very high maximum latency and an overall higher average latency, that can be indicative of a device/host issue. Even with an SSD kicking out an appreciably higher maximum latency the result would have to be in conjunction with higher overall latency to indicate a problem.

The average latency is important, but having a very fast SSD is only good if there are not long hangs for individual file requests.

The 120GB 840 exhibits a surprising read latency weakness in this test. The maximum latency of over 31ms is not expected, especially when taking into consideration that the write speed tends to be the weakness of these new TLC SSDs. We did repeat this test several times, and this was among the best results with regards to maximum read latency. This result is 3 times higher than the nearest competing solution. Users can expect long hangs and lags such as this to have a tangible impact upon OS and application performance.

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Maximum Write Latency takes into account the longest single read access (file) that is requested during the duration of the test. The maximum write latency also is more than 3 times that of the nearest competitor. This is indicative of either some type of firmware issue, or the underlying NAND not responding well to the lack of parallelism that more capacity brings with it. This again will result in hiccups in performance that can leave users staring at a spinning blue circle.