Samsung 970 Evo review

Samsung unveiled the 960 Evo NVMe drive back in September 2016 and, along with it, the insanely fast 960 Pro series. For those PC owners wanting to exceed the speed limits of SATA, these drives offered gigabytes per second read and writes using the M.2 NVMe PCIe interface.

Now Samsung has launched the 970 Evo, but is it more of the same, marginally better or a significant boost from the 960? Let’s find out.

Price & availability

The price for the 1TB model is  £375.79 from Amazon, and it looks likely to remain at that level for a while. That’s only a fiver less than the previous 960 Evo 1TB, suggesting that Samsung thinks the 970 EVO is worth just as much.

In the US it costs $525.95 from Amazon.com.

There are other capacities of course, with 250GB, 500GB and 2TB options costing £100.79 / US$109.99, £193.79 / US$249.08 and £709.99 respectively. A quick calculation reveals that the larger drive you get the lower the cost per GB they are, making the 2TB the best value and the 250GB the least.

The Intel 1TB 600P is cheaper, but isn’t in the same performance envelope. ADATA has the SX8000 with similar performance to the 600P, but is asking another 20 percentfor it. Plextor is in the same boat with the M9PeG 1TB, a drive that has been overtaken by developments.

Ironically, much of the initial competition for the 970 Evo is likely to come from older Samsung products as older models become discounted to clear old stock – so watch out for bargain 960 Evo drives.

The other threat comes from Western Digital, and other SSD makers willing to leverage the 64-bit NAND that Micron and Toshiba are providing to many brands. While the price of NVMe storage is stubbornly high, Samsung can do well with the 970 Evo, but that scenario won’t last forever.

Features and design

All M.2 NVMe drives look almost identical, so there is little point discussing the aesthetics of the 970 Evo compared with any other.

It’s inside where the action is, and comparing the new design to its 960 Evo predecessor, there are some notable changes. The prior 960 Evo used the cheaper TLC V-NAND, where the 970 Evo uses MLC V-NAND, the same expensive flash technology with which the 960 Pro was blessed.

Being closer to the Pro design, the 970 Evo should outperform the 960 Evo easily, but will it also eclipse the 960 Pro?

The success of any SSD design is determined by how the controller and cache memory are integrated with the NAND modules, and how effectively that fusion allows their true performance to be exploited.

Where the 960 Evo used up to 1GB of LPDDR3 memory for its cache, the new 970 Evo uses LPDDR4 memory, and on the 2TB drive it has 2GB of that available.

Using a new memory model has required a new controller, and Samsung has introduced the Phoenix to replace the Polaris controller used on the 960 Evo.

The upshot of these changes is that where the 960 Evo maxed out at 3,200MB/s reads and ranged from 1,500 MB/s to 1,900MB/s writes (dependent on drive capacity). The 970 Evo is quoted as offering 3,400-3,500MB/s writes and reads that go from 1,500MB/s on the 256GB model, up to 2,500MB/s on the 1TB and 2TB options.

IOPS across the board are also massively boosted with the 1TB and 2TB 970 Evo delivering a massive 500k read IOPS on QD 32 four thread testing. That’s 31 percent more IOPS than the best the 960 Evo could achieve, and it manages this while only using 0.3 watts extra power.

Enough of the claimed figures… how does it perform on our bench tests?

Samsung 970 Evo benchmarks

Samsung kindly provided us with a 1TB 970 Evo for testing.  The fly in this ointment was a new PCIe NVMe driver that Samsung provided which altered the way that the 970 EVO worked and caused us to question the validity of our results.

In many tests, the drive worked precisely as predicted, but in other applications it underperformed for no obvious good reason.

We eventually concluded that these discrepancies are side effects from the organisation of the buffers in this device to negate the impact of random write traffic striking when the drive is least able to handle it.

The TurboWrite buffer is designed to reduce the impact of very large files being thrown at the device, which on the previous 960 Evo caused the drive to write at speeds on par with SATA SSD speeds.

The 960 Evo did have a TubroWrite buffer, but it didn’t seem to work as well as the one on the 970 Evo for handling really big file writes.

On the 970 Evo, the TurboWrite buffer is 6GB by default on the 1TB model and an additional 36GB that it can dynamically open up if you throw everything including the kitchen sink at the drive.

The the cache is smaller on the smaller 250GB and 500GB models, and the amount of Intelligent reserve scales to up to 72GB on the 2TB drive. Therefore if you are editing video, for example, the 2TB drive has a TurboWrite total space of 78GB, where the 1TB only has 42GB.

Once you hit these limits the 2,500MB/s writing drops to 1,200MB/s on the 1TB, and just 300MB/s and 600MB/s on the 250GB and 500GB drives respectively.

The AS SSD benchmark version 1.9 could also create the same effect by disabling buffers, and under that situation the previous 960 Evo 1TB would only write at 400MB/s.

That problem looks effectively fixed in the 970 Evo because on that test write performance was a sustained 2,245MB/s, very little below its normal operating levels. And without sending a file of more than 42GB in size, this is the performance that Samsung claims.

However, in the same test read speed suffered without buffers, showing how solving one problem might have created another elsewhere.

With buffers active, the default scenario, read speeds on CrystalDiskMark 6.0 hit a blistering 3,571MB/s and write was equally impressive 2,497 MB/s. That test is revealing for small file sizes, exactly where the 970 Evo excels.

Overall, these are impressive numbers and eclipse the previous 960 Evo, and the 2TB 960 Pro we’ve both previously tested.

The only real concern for Samsung is likely to be in which direction to go from here. Without using more than four PCIe channels, there is very little additional bandwidth on reading speed to exploit.

The next generation of drives might use less power and offer greater capacities, but they’re unlikely to be going much faster than the 970 Evo and 970 Pro.

Tests we can’t do

There is one set of tests we’d love to do, but don’t have the resources to allocate to finding out where the limit is for total bytes written.

Accepting the quoted numbers, the 970 Evo has dramatically better TBW (Total Bytes Written) than the 960 Evo, making it more suitable for those situations where the drive has large amounts of data regularly written to it.

The 1TB model reviewed here has a 600TB lifespan and the 2TB model doubles that value to 1,200TB. In both cases, that’s plenty of new files written, every day, for years and years.

At each capacity that’s 50 percent more bytes written over the life than the 960 Evo, though it slightly lags the 960 Pro by 25 percent until it hits the 2TB capacity.

The 970 Pro doesn’t have a 2TB option currently, so the lifespan of the 2TB 970 Evo is the best on offer until Samsung releases a 2TB Pro at that size.