For years, Intel SSDs have been bound by the constraints of the Serial ATA interface. But they suffer no longer. Intel has unveiled a deep lineup of PCI Express SSDs. The drives are targeted at datacenters and servers, and they're split three ways. The DC P3700 Series is designed for write-intensive environments, the DC P3600 Series is meant for mixed workloads, and the DC P3500 Series is best for read-dominated tasks. Intel wants to provide a broad range of options to suit customers with different needs and budgets.
All the drives hook into the host system via a four-lane PCIe 3.0 interface with 4GB/s of bandwidth. There are two different form factors: a half-height expansion card and a SATA-style 2.5" case with an SFF-8639 connector. The SFF connector is compatible with SAS, SATA, and PCIe drives, and Intel's next-gen Xeon platform will support it natively.
The DC P-series SSDs eschew SATA's AHCI legacy in favor of the NVM Express protocol, which was designed explicitly for PCIe drives with non-volatile memory. NVMe brings much deeper command queues—and a lot more of them. The streamlined protocol also has lower CPU overhead, a particularly important factor for datacenter applications. NVMe support is built into the Linux kernel, and it's also in Windows Server 2012 R2 and Win8.1.
A proprietary Intel controller powers the new PCIe SSDs. The chip has an eight-channel NAND interface that's very similar to the one in the company's SATA-based server drives. The firmware is all Intel's own, as well. As one might expect, the P-series SSDs have all the hallmarks of enterprise-oriented products: full end-to-end data protection, power-loss protection, and parity-based die redundancy.
Intel uses 20-nm MLC NAND throughout the lineup, but only the P3700 Series' flash memory is pulled from high-endurance stock. The P3600 has "mid"-grade NAND, while the P3500 uses standard stuff. That lower-grade NAND has less endurance, which is reflected in the official specifications. The P3700 is good for up to 36.5 petabytes of total writes, Intel says, but the P3600 maxes out at 10.95PB, and the P3500 is only rated for 1PB. All three have five-year warranty coverage.
|DC P3700 Series||DC S3600 Series||DC P3500 Series|
|Capacities||400, 800GB, 1.6, 2TB||400, 800GB, 1.2, 1.6, 2TB||400GB, 1.2, 2TB|
|64KB Sequential read||2800MB/s||2600MB/s||2500MB/s|
|64KB Sequential write||1900MB/s/s||1700MB/s||1700MB/s|
|4KB Random read||460k IOps/s||450k IOps||450k IOps|
|4KB Random write||180k IOps/s||70k IOps||35k IOps|
|4KB Random 70/30 mix||250k IOps||170k IOps||85k IOps|
|Max writes||36.5 PB||10.95PB||1PB|
|Max drive writes/day||10||3||0.3|
In addition to being the Ironman of the bunch, the P3700 is the fastest. The drive is rated for sequential reads up to 2800MB/s and writes up to 1900MB/s. The other models mostly keep up on the sequential front. However, their random I/O rates are much lower with writes and mixed workloads.
Some P-series goodness is on its way to our labs, but it hasn't arrived yet, so we haven't been able to run our own tests. For what it's worth, Intel claims the drives offer better—and more consistent—performance than their peers.
Capacities top out at 2TB for all three variants. Depending on the amount of storage, power consumption is supposed to be around 11-12W for sequential reads and 20-25W for sequential writes. The drives rely entirely on the PCIe interface for power.
The P-series SSDs aren't exactly cheap, but server SSDs rarely are, and the total cost of ownership matters more than the purchasing price for this sort of product. Compared to its SATA counterpart, the DC P3700 looks like a relative bargain. DC S3700 sells for $875, but its performance ratings are several times lower than those of the P3700. In fact, Intel contends that a single P3700 has higher read performance than six S3700 drives in RAID.
Intel plans to begin mass production of its PCIe datacenter SSDs later this month. The first drives will start rolling out in the third quarter, and it sounds like the launch will be a staggered one, with different models and capacities arriving at different times.