The New Indirection Table

While the binary tree structure was great for sequential IO performance and for keeping DRAM sizes low, it wasn't good for lowering random IO latency. The S3700 controller completely does away with the old indirection table.

The new controller ditches the binary tree entirely and moves to a completely flat structure with 1:1 mapping. What happens now is there's a giant array with each location in the array mapped to a specific portion of NAND. The array isn't dynamically created and, since it's a 1:1 mapping, searches, inserts and updates are all very fast.

The other benefit of being 1:1 mapped with physical NAND is that there's no need to defragment the table, which immediately cuts down the amount of work the controller has to do. Drives based on this new controller only have to keep the NAND defragmented.

The downside to all of this is the DRAM area required by the new flat indirection table. The old binary tree was very space efficient, while the new array is just huge. It requires a large amount of DRAM depending on the capacity of the drive. In its largest implementation (800GB), Intel needs a full 1GB of DRAM to store the indirection table. By my calculations, the table itself should require roughly 100MB of DRAM per 100GB of storage space on the drive itself. Intel appears to be using DDR3-1333 for its DRAM on-board S3700 drives.

There's a bit of space left over after you account for the new indirection table. That area is reserved for a cache of the controller's firmware so it doesn't have to read from slow flash to access it.

Once again, there's no user data stored in the external DRAM. The indirection table itself is physically stored in NAND (just cached in DRAM), and there are two large capacitors on-board to push any updates to non-volatile storage in the event of power loss.

It sounds like a simple change, but building this new architecture took quite a bit of work. The results, if they are anywhere close to what Intel is promising, are pretty awesome.

Final Words

The Intel SSD DC S3700 appears to be a very promising new architecture from Intel. If it ends up performing as Intel promised, the S3700 controller could be the beginning of a new era in SSD performance - one focused on consistency of performance, not just absolute performance. As soon as we run samples through our test suite you can expect a full review, putting Intel's claims to the test. Stay tuned.

A Brand New Architecture & The Old Indirection Table
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  • blackbrrd - Monday, November 5, 2012 - link

    Sounds like a huge improvement for databases. The write endurance looks phenomenal! Reply
  • FunBunny2 - Monday, November 5, 2012 - link

    What he said!! Reply
  • Guspaz - Monday, November 5, 2012 - link

    I'm saddened by the increasingly enterprise-oriented focus of Intel. Their SSDs have quite a good reputation in consumer circles as providing reliable performance and operation, and their latest product line (the 330 series) definitely has consumer-level pricing. They're currently sitting at $0.78/GB on the 240GB model, which is pretty competitive with the rest of the market.

    The nice thing was that Intel is the safe bet; if you don't want to sort through all the other stuff on the market, you can feel pretty safe buying an Intel. Yes, they've had issues, but generally less than other SSD manufacturers. But with pricing like the S3700 is featuring, the days of Intel being competitive in the consumer space may be over...

    I'd rather see Intel take a two-tiered approach. By all means, keep putting out the enterprise drives for the high margins, but also keep a toe in the consumer market; they'll get a good deal of sales there based on their reputation alone.
    Reply
  • karasaj - Monday, November 5, 2012 - link

    Just because this is an enterprise SSD doesn't mean that Intel is 100% abandoning the consumer market y'know. They can focus on enterprise but still release consumer SSDs. Reply
  • martyrant - Monday, November 5, 2012 - link

    $235 at launch for a 100GB performance SSD will not seem too bad to the enthusiast "consumer" circle. That will, of course, drop over time, and bring it within the means of even more budget minded enthusiasts. It was not long ago people were shelling out $200-250 for 80GB Intel X-25M / G2s. I still have two in RAID 0 that I just replaced this last weekend with 4x128GB Samsung 830s in RAID 0 (for $70/piece, that's not a bad 512GB [unformatted] setup). My girlfriend's PC is inheriting the G2's. While $235 for 100GB is still on the high end, I'm sure there will be people who will pay that in the consumer market when they launch if they really do solve some of the IO issues (I have noticed quite a few with Windows 8, not so much in Windows 7 remarkably...but Win8 has serious DPC issues to begin with). Reply
  • Omoronovo - Monday, November 5, 2012 - link

    Windows 8 has no DPC issues. There are no updated applications that can measure DPC correctly with the deferred timing in the Windows 8 kernel, making it appear to have a constant/high DPC.

    Additionally, DPC latency has nothing to do with disk accesses. Disk accesses are not a function of interrupts in the kernel, unlike audio and video.
    Reply
  • Kjella - Monday, November 5, 2012 - link

    With the market going to even smaller process sizes and TLC the drives can't take enthusiast use anyway, my SSD life meter tells me my drive is going to die after 3.5 years - and that's after I worn out one in 1.5 years being nasty with it. Right now my C: drive is 83GB... 100GB is maybe cutting it a little short, I'd like at least 150GB, but otherwise yeah this is a drive I could want. Reply
  • ExarKun333 - Monday, November 5, 2012 - link

    Much of the enterprise offerings end-up trickling down to consumer products. Just be patient. :) Reply
  • Beenthere - Monday, November 5, 2012 - link

    No offense intended but it's totally inaccurate to state that "Intel is the safe bet". They have had issues with their consumer grade SSDs like most other SSD suppliers who rush products to market without proper validation. I would not trust an Intel SSD any more than most of the other drives with few exceptions. Until an SSD company proves their product in fully compatible, reliable, doesn't change size or lose data, or disappear from they system, I'm not buying the hype.

    I'm from Missouri - the SHOW ME state.
    Reply
  • martyrant - Monday, November 5, 2012 - link

    So are you speaking from personal experience with Intel SSDs since you are from the "SHOW ME" state?

    I have 4 Intel SSDs (two G2s, two 320s) and have had zero issues with them. I bought four OCZ Vertex 4s a little over a month ago and returned all four of them because of compatibility issues and consistently appearing/disappearing in single and RAID configurations in multiple computer setups. I'd also owned a 64GB OCZ V2 that I've since given away (RMA'd it 3 times it kept dying, didn't care to bother with it after that). I have had zero issues with the Intel SSDs and am hoping to find the same reliability with the 830s I just upgraded to.

    Also, if you actually looked / did some research you would find that Intel has had a lot less issues (even though they have had some of the same Sandforce issues as other mfgs) than other companies....sometimes claiming you sit around waiting for someone to "SHOW" you the proof it sounds like you are couch potato who still cares who wins the election because you actually think one is different than the other...and msnbc/cnn/fox/history/discovery/comedy central told you so (just saying, going out and gathering your own empirical information is worth it sometimes).
    Reply

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