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Samsung 950 Pro SSD Review

NVMe in the M.2 form factor is finally a reality for desktop enthusiasts. Retailers begin selling Samsung's 950 Pro today, and we already have three drives in-hand.

Initial Performance Results

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Entropy (a fancy way of saying the level of incompressible data) does not affect performance on the 950 Pro. That's good news for enthusiasts working with media files, which are typically already compressed.

Samsung's 950 Pro doesn't rely on TurboWrite to burst high levels of write performance. Instead, it delivers consistent sequential and random throughput by virtue of its MLC NAND. In the above screen shot, I wrote 64KB sequential blocks to the drive's full LBA range, observing minimal deviation between the high and low results. TLC-based drives often start out with impressive write speed, and then abruptly give up their strong performance when the emulated SLC cache many of them use fills up.

To read about our storage tests in-depth, please check out How We Test HDDs And SSDs. Four-corner testing is covered on page six.

Sequential Read Performance

As mentioned, we're testing both capacities, along with two 512GB 950 Pros in RAID 0. For comparison, we include Kingston's HyperX Predator 480GB, Intel's SSD 750 400GB and 1.2TB, as well as the latest 2TB 850 Pro.

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Right off the bat, Samsung's 950 Pro drives outperform the SSD 750s in sequential reads at low queue depths. Intel's SSD 750s also experience an odd performance drop at a queue depth of two. This may be fixed in the firmware Intel recently released, though we haven't had the chance to re-test with it yet.

Around a queue depth of 16, Intel's 1.2TB model overtakes the 512GB 950 Pro in our sequential read test. But the 400GB SSD 750 never passes Samsung's largest 950 Pro.

The 950 Pros in RAID 0 run away from the rest of the field. That's a result we'd expect in a test moving data sequentially.

Remember, the 850 Pro 2TB can only be tested up to a queue depth of 32; that's the SATA interface's limit.

Sequential Write Performance

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The 512GB 950 Pro and RAID 0 array charge forward with class-leading sequential write performance. And you don't need a taxing workload to realize these results, either. The 950 Pro 256GB falls back in the pack, though its performance is still better than we expected, given the smaller capacity point.

Random Read Performance

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From a queue depth of one to 16, Samsung's 950 Pros outperform the other drives we tested. At a queue depth 32 and up, Intel's data center DNA kicks in, giving the SSD 750 an advantage. But in client workloads where low queue depths are involved, the 950 Pro is unrivaled.

If you paid close attention to Samsung's specs, then you already noticed that our random read results fall below the company's claimed 300,000 IOPS. NVMe can queue data a couple of different ways to optimize performance. Samsung's large random read numbers are derived from four workers, each several queues deep. That's a great way to show what NVMe can do. However, until desktop software can emulate that scenario, we'll continue testing under more realistic conditions.

Random Write Performance

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Intel's SSD 750 wears the random write performance crown. Two 950 Pros in RAID 0 close the gap, but single-drive random writes go Intel's way. Under a normal load, you won't hit these ceilings (particularly at a queue depth of one). Latency is what's important here, and higher performance at low queue depth translates to low latency results.

Chris Ramseyer is a Contributing Editor for Tom's Hardware US. He tests and reviews consumer storage.