Solid state storage has quickly been able to saturate the SATA interface just as quickly as new standards are introduced. The first generation of well-built MLC SSDs quickly bumped into the limits of 3Gbps SATA, as did the first generation of 6Gbps MLC SSDs. With hard drives no where near running out of headroom on a 6Gbps interface, it's clear that SSDs need to transition to an interface that can offer significantly higher bandwidth.

The obvious choice is PCI Express. A single PCIe 2.0 lane is good for 500MB/s of data upstream and downstream, for an aggregate of 1GB/s. Build a PCIe 2.0 x16 SSD and you're talking 8GB/s in either direction. The first PCIe 3.0 chipsets have already started shipping and they'll offer even higher bandwidth per lane (~1GB/s per lane, per direction).

PCI Express is easily scalable and it's just as ubiquitous as SATA in modern systems, it's a natural fit for ultra high performance SSDs. While SATA Express will hopefully merge the two in a manner that preserves backwards compatibility for existing SATA drives, the server market needs solutions today.

In the past you needed a huge chassis to deploy an 8-core server, but thanks to Moore's Law you can cram a dozen high-performance x86 cores into a single 1U or 2U chassis. These high density servers are great for compute performance, but they do significantly limit per-server storage capacity. With the largest eMLC drives topping out at 400GB and SLC drives well below that, if you have high performance needs in a small rackmount chassis you need to look beyond traditional 2.5" drives.

Furthermore, if all you're going to do is combine a bunch of SAS/SATA drives behind a PCIe RAID controller it makes more sense to cut out the middleman and combine the two.

We've seen PCIe SSDs that do just that, including several from OCZ under the Z-Drive and RevoDrive brands. Although OCZ has delivered many iterations of PCIe SSDs at this point they all still follow the same basic principle: combine independent SAS/SATA SSD controllers on a PCIe card with a SAS/SATA RAID controller of some sort. Eventually we'll see designs that truly cut out the middlemen and use native PCIe-to-NAND SSD controllers and a simple PCIe switch or lane aggregator. Micron has announced one such drive with the P320h. The NVMe specification is designed to support the creation of exactly this type of drive, however we have yet to see any implementations of the spec.

Many companies have followed in OCZ's footsteps and built similar drives, but many share one thing in common: the use of SandForce controllers. If you're working with encrypted or otherwise incompressible data, SandForce isn't your best bet. There are also concerns about validation, compatibility and reliability of SF's controllers.

Similar to its move into the MLC SSD space, Intel is arriving late to the PCIe SSD game - but it hopes to gain marketshare on the back of good performance, competitive pricing and reliability.

The first member of the new PCIe family is the Intel SSD 910, consistent with Intel's 3-digit model number scheme.

The 910 is a single-slot, half-height, half-length PCIe 2.0 x8 card with either 448GB or 896GB of Intel's 25nm MLC-HET NAND. Part of the high endurance formula is extra NAND for redundancy as well as larger than normal spare area on the drive itself. Once those two things are accounted for, what remains is either 400GB or 800GB of available storage.

The 910's architecture is surprisingly simple. The solution is a layered design composed of two or three boards stacked on one another. The first PCB features either two or four SAS SSD controllers, jointly developed by Intel and Hitachi (the same controllers are used in Hitachi's Ultrastar SSD400M). These controllers are very similar to Intel's X25-M/G2/310/320 controller family but with a couple of changes. The client controller features a single CPU core, while the Intel/Hitachi controller features two cores (one managing the NAND side of the drive while the other managing the SAS interface). Both are 10-channel designs, although the 910's implementation features 14 NAND packages per controller.