The SSD 850 Evo is Samsung’s second consumer drive after the 850 Pro that uses its 3D V-NAND technology no other manufacturer yet has a 3D NAND-based SSD available.
The 850 Evo has just four capacities now (120GB is the fourth), with each capacity available in a single SKU that comprises the drive and software CD. For now, at least, they’re only available as 2.5in SATA 6Gbps drives.
Samsung has developed a new SSD controller, the dualcore MGX, which has one less ARM Cortex R4 core and four less channels than the triple-core MEX controller in the 840 Evo and 850 Pro.
As such, you’d expect performance to drop, but thanks to the use of Samsung’s 3D V-NAND and firmware optimisations, Samsung says the speed has slightly improved, although the biggest improvements should be felt in lower-capacity drives.
However, the 1TB 850Evo still sticks with the MEX controller, since it requires 1GB of DRAM cache in order to manage the page table for so much NAND, and the MGX controller only supports up to 512MB, as used in the 250GB and 500GB drives.
Samsung’s current 3D V-NAND technology stacks NAND cells vertically with 32 layers, bypassing the limitations and drawbacks associated with constantly shrinking current 2D/planar technologies. The performance, endurance and efficiency are all improved, so the only downside is cost of production.
In order to bring the technology to a lower price, the 3D NAND in the SSD 850 Evo can store three bits per cell rather the SSD 850 Pro’s two bits. Traditionally, this limit decreases NAND endurance, but the endurance is already so high that Samsung is guaranteeing the same 150TB write limit as the SSD 850 Pro, albeit within a five-year warranty, not ten.
Increasing the bits-per-cell count also decreases write performance, but Samsung counters this limit with its TurboWrite buffer. All write commands pass through the buffer, which is again 3GB (250GB), 6GB (500GB) and 12GB (1TB) in size. It acts as SLC NAND (one bit per cell), dramatically increasing performance.
If a single command exceeds this buffer then performance will drop as the writes go direct to the TLC NAND, but idle periods are used to clear the buffer. It’s a good system for most people, since most of us don’t regularly write more than this amount. Also, post-TurboWrite speeds aren’t that low anyway.
Once again, Samsung’s SSD software package (Magician and Data Migration) remains unrivalled. The intuitive interfaces allow for easy OS cloning, firmware updates, secure erase commands and overprovisioning. You can also easily enable and disable the excellent RAPID Mode, which uses spare RAM to cache data for ultra-fast performance, and implement any of the SSD 850 Evo’s encryption features, including AES 256-bit, IEEE-1667 and TGC Opal 2.
Performance
Few SSDs struggle with sequential performance now, but even so, the SSD 850 Evo excels here, never dipping below 500MB/sec for reads or writes. Random 4KB read speeds are also the best we’ve seen (dethroning the 840 Evo as the previous best). As for writes, OCZ’s drives are a touch faster, but the 850 Evo drives’ performance is still very good.
We also noticed that the MGX-based 250GB and 500GB models are slightly faster in these benchmarks than the MEX-based 1TB, lending weight to Samsung’s claims that the controller is optimised for such workloads, which are particularly important for everyday office tasks.
Next came the particularly strenuous high-queue-depth random tests, but the SSD 850 Evo drives handled them well, being faster than the Crucial MX100. However, everyday users need not concern themselves with these demanding workloads.
Meanwhile, the PCMark 7 Starting Applications workload shows the 850 Evo improving by at least 11 per cent over the 840 Evo, and just about beating the MX100. There’s less of an improvement in the gaming test, but the results still impress and again, the performance is more or less constant regardless of capacity, while still being a fair way in front of the Crucial MX100.
The drives boot Windows 7 quickly too, with the 250GB model having a very impressive boot time indeed – lower capacities typically fare best in this test, and the 1TB drive performed less well.
Finally, the 500GB drive improves by over 50 per cent on average in the Iometer mixed workloads tests, where the other two drives also do well. These tests are run at a high queue depth, so these drives would cope in relatively demanding professional environments.
However, for such users there are even better SSDs that are worth their extra premium if you’re going to be hammering your drive constantly (including Samsung’s own SSD 850 Pro range).
SPECS:
| MZ-75E120B/AM | MZ-75E250B/AM | MZ-75E500B/AM | MZ-75E1T0B/AM | |
|---|---|---|---|---|
| Capacity | 120GB | 250GB | 500GB | 1TB(1000GB)* |
| Sustained Sequential Read | Up to 540MB/sec | Up to 540MB/sec | Up to 540MB/sec | Up to 540MB/sec |
| Sustained Sequential Write | Up to 520MB/sec | Up to 520MB/sec | Up to 520MB/sec | Up to 520MB/sec |
| Random Read @ 4KB/QD32 | 94000 | 97000 | 98000 | 98000 |
| Random Write @ 4KB/QD32 | 88000 | 88000 | 90000 | 90000 |
| Product Type | 2.5 inch SATA III Solid State Drive | 2.5 inch SATA III Solid State Drive | 2.5 inch SATA III Solid State Drive | 2.5 inch SATA III Solid State Drive |
| Controller | Samsung MGX Controller | Samsung MGX Controller | Samsung MGX Controller | Samsung MEX Controller |
| NAND Flash Memory | Samsung 32-Layer 3D V-NAND | Samsung 32-Layer 3D V-NAND | Samsung 32-Layer 3D V-NAND | Samsung 32-Layer 3D V-NAND |
| Warranty | 5 Years/150TBW | 5 Years/150TBW | 5 Years/150TBW | 5 Years/150TBW |
Conclusion
The cost of producing 3D V-NAND leaves the SSD 850 Evo drives with mid-range prices, which is dangerous ground – typically, people either want expensive professional drives with outstanding performance and endurance for intensive workloads, or simply the best cost per gigabyte and decent everyday performance.
Most people could save $50-55 and get the Crucial MX100 512GB without noticing any performance difference in everyday use.
However, the Evo 850s are still excellent SSDs. With outstanding software, speed-enhancing features such as TurboWrite and RAPID Mode, and a warranty that’s two years longer than the 840 Evos, they offer a great package.
However, their relatively high prices mean they’re only recommended for heavily storage-dependent workloads, or if you want extra control via the Magician software.
Where to Buy
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