Inside Intel's SSD DC S3700
We peeled the cover off of our 200 and 800 GB samples to get a better sense of hardware Intel is using. On both drives, it's easy to spot the new 6 Gb/s PC29AS21CA06 Gb/s controller. Again, it employs an eight-channel architecture instead of the 10-channel design used previously.
On the 800 GB drive, the controller is flanked by a pair of 4 Gb Samsung DDR3-1600 FBGA RAM packages, totaling 1 GB of cache. Below the controller, you see eight NAND packages, each adding 64 GB of capacity. The other side of the drive features eight more, pushing the 800 GB model's total capacity up to 1 TB.
The 200 GB version is configured quite a bit differently. The layout and controller are almost identical, but as you can see, there's a single 2 Gb DDR3 cache chip from Micron, rather than the two 4 Gb Samsung packages.
You still find 16 total NAND packages on-board. However, their densities aren't uniform. Fourteen of them are 16 GB chips, one adds 32 GB, and one is an 8 GB part, totaling 264 GB.
One of the SSD DC S3700's more unique enterprise-oriented features is the use of capacitors to maintain data integrity during a power failure. Two 35 V, 47 uF capacitors store enough charge to commit all data in the write cache to NAND. The radial electrolytic capacitors are bent into a cutout in the PCB, allowing Intel to free up board space that would have been needed for surface-mount capacitors.
Intel also incorporates sensor logic that periodically checks capacitor health. Any outright failure, or even degraded performance, triggers a SMART event and disables write caching to counter the risk of data loss.
Another first for Intel is utilization of the SATA connector's 12 V rail. In fact, the SSD DC S3700 can operate on +5 V, +12 V, or both. Granted, using the +12 V rail does increase power draw, but we'll go into more detail on that in the power consumption analysis.
SSD DC S3700 Write Endurance
We typically spend a lot of time testing the write endurance of enterprise-oriented SSDs. Why? It's a big reason the highest-end SSDs cost so much more than the client-oriented stuff.
Intel uses the same 25 nm HET-MLC on its SSD DC S3700 that it put in the SSD 710 and 910. In fact, the company gives an identical write endurance spec for its 400 and 800 GB SSD DC S3700 and SSD 910 drives. There may be some differences in the way Intel's new controller handles TRIM and garbage collection, but they're likely very small.
| Endurance RatingSequential Workload, QD=1, 8 MB, Random | Intel SSD DC S3700 | Intel SSD 710 | Intel SSD 910 |
|---|---|---|---|
| NAND Type | Intel 25 nm HET-MLC | Intel 25 nm HET-MLC | Intel 25 nm HET-MLC |
| RAW NAND Capacity | 264 GB | 320 GB | 896 GB |
| IDEMA Capacity (User Accessible) | 200 GB | 200 GB | 800 GB |
| Over-provisioning | 32% | 60% | 12% |
| P/E Cycles Observed (IDEMA) | 36,343 | 36,600 | 46,339 |
| P/E Cycles Observed (Raw) | 27,532 | 22,875 | 41,374 |
| Host Writes per 1% of MWI | 72.69 TB | 73.20 TB | 370.71 TB |
| $/PB-Written | $64.66 | $181.72 | $106.60 |
Based on its over-provisioning and lower cost, the SSD DC S3700's cost per petabyte written is extremely low for an MLC-based drive. Of course, it cannot compete with the extreme endurance rating of SLC flash. Drives like Micron's RealSSD P320h reign supreme at less than $40 per petabyte written.
Will that change in the near future? If Intel manages to push the price of HET-MLC drives down to $1.40/GB (a 40% reduction from current prices), it would match the Micron drive in dollars per petabyte written. Considering the recent price history of Intel's HET-MLC-based drives and the rather static pricing of SLC-based devices in general, it doesn't seem far-fetched to anticipate this in the next 12 months.