When Intel launched their first new SSD controller in years, it took the form of the high end enterprise drive, the DC S3700. The focus was on performance consistency over just about anything else, and it handled its steady state transition better than any drive we’ve ever tested.
However because it used very expensive high endurance 25nm NAND, with a lot of it over-provisioned (to attain said consistency), it may be considered too costly for a many of applications. Even though it is available in capacities as low as 100GB usable, that drive still costs $250. And not all applications call for such a high performance drive, or need such durable flash.
In our review of the DC S3700, I speculated that the same controller could be paired up with cheaper flash with less of it overprovisioned, to create a product that sits in a different price range and market segment. The DC S3500 we’re reviewing today is just that. The same Intel PC29AS21CA controller is being used, this time paired up with 20nm MLC flash. This essentially the ‘read oriented’ version of the DC S3700. Applications like web servers and cloud servers do not need so much write performance and durability, so the DC S3500 is potentially the perfect fit.
Intel DC S3500 vs DC S3700
The differences between the two models are few – the NAND used is different, and because of that, expected performance changes, as does the Total Bytes Written:
Intel DC S3500 | Intel DC S3700 | |
|---|---|---|
| Price (Bulk) | 80GB: $105 120GB: $145 160GB: $189 240GB: $279 300GB: $355 480GB: $579 600GB: $724 800GB: $979 | 100GB: $235 200GB: $470 400GB: $940 800GB: $1880 |
| NAND Type | 20nm MLC | 25nm HET MLC |
| Sequential Transfer Read/Write MB/s | 80GB: 340 / 100 120GB: 445 / 135 160GB: 475 / 175 240GB: 500 / 260 300GB: 500 / 315 480GB: 500 / 410 600GB: 500 / 410 800GB: 500 / 450 | 100GB: 500 / 200 200GB: 500 / 365 400GB: 500 / 460 800GB: 500 / 460 |
| Random 4K Transfer Read/Write IOPS | 80GB: 70,000 / 7,000 120GB: 75,000 / 4,600 160GB: 75,000 / 7,500 240GB: 75,000 / 7,500 300GB: 75,000 / 9,000 480GB: 75,000 / 11,000 600GB: 75,000 / 11,000 800GB: 75,000 / 11,500 | 100GB: 75,000 / 19,000 200GB: 75,000 / 32.000 400GB: 75,000 / 36,000 800GB: 75,000 / 36,000 |
| Total Bytes Written | 80GB: 45 TB 120GB: 70 TB 160GB: 100 TB 240GB: 140 TB 300GB: 170 TB 480GB: 275 TB 600GB: 330 TB 800GB: 450 TB | 100GB: 1.825 PB 200GB: 3.65 PB 400GB: 7.3 PB 800GB: 14.6 PB |
| Read / Write Latency | 50 µs / 65 µs | 50 µs / 65 µs |
| MTBF | 2 Million Hours | 2 Million Hours |
The combination of denser NAND being inherently less durable than that made on a larger manufacturing process, and the DC S3700 using “HET” MLC makes the TBW (Total Bytes Written) portion of this chart stand out more than usual. Indeed, the S3700 measures its TBW spec in petabytes, while the S3500 uses the more standard terabytes. Compared to other SSDs using standard 25nm NAND though, the S3500 fares pretty well. For instance, the 256 GB OCZ Vector has a TBW of 36.5 TB, according to OCZ. The 20nm Intel SSD 335 has a TBW of 32TB at 240GB.
As for expected performance, the S3500 is also lower than the S3700, at least in terms of write ops. Also note that because of the smaller process, full performance isn’t attained until capacity reaches 480 GB. The S3700 (and most other SSDs using 25nm flash) can usually reach peak performance at around 240 GB. This is because as the manufacturing process shrinks, the number of NAND die per chip decreases. For full performance, an SSD’s controller must be fully saturated with interpolated data. 25nm flash can contain up to 8 die per chip, while 20nm is down to 4. So while cost per chip is reduced quite a bit, more total capacity is needed to reach full performance.
