Intel DC P3520 Enterprise SSD Review

Intel Rolls Its 3D MLC NAND Into The Data Center

Intel designed its new DC P3520 to accelerate the goodness of NVMe and 3D NAND to a broader spate of read-centric data center applications with an extremely competitive price point. Intel's DC P3520 series brings the price of bleeding-edge NVMe technology down to ~$0.55 per GB, which is within striking distance of enterprise SATA SSDs.

The early days of enterprise SSDs were tedious and expensive times. Manufacturers developed their own customized drivers and software for each new SSD, which increased costs and lengthened qualification cycles. The interoperability minefield was a perilous journey for OEMs and end users, so the industry welcomed the standardized NVMe interface with wide-open arms. NVMe is widely known for its stellar performance, but the interface also brought us the promise of commodity SSDs. Now even hyperscale data centers create their own SSDs with relative ease.

NVMe helped to lower cost and foster adoption, but expensive NAND held the industry back. The pricing picture became brighter with each new planar lithography shrink, but denser and cheaper 2D NAND brought the undesirable side effects of less endurance and performance. 3D NAND circumvents the four primary barriers of price, endurance, power, and performance in one fell swoop. Samsung led the 3D NAND race and enjoyed an exclusive advantage for several years, but now IMFT's (Intel/Micron) 3D NAND is barreling into the data center. The increased competition will likely be the key to unlocking the true promise of a commodity-like marketplace.

In many respects, the DC P3520 is simply a re-spin of Intel's venerable DC P3x00 series with updated NAND and improved endurance, but unlike the current trend of delivering ultra-endurant SSDs as the lead vehicle, Intel chose to start its 3D journey with low-endurance products. The strategy makes sense, because data center operators are employing SSDs into mainstream workloads as prices continue to plummet, so the volume play resides on the low end of the endurance totem pole.

Intel employed its 20nm HET MLC in its previous-generation P3x00 PCIe and DC Sx00 SATA series, but the march of NAND progress has many other vendors still forging ahead with products based on 15nm and 16nm planar NAND. For instance, Micron also benefits from the IMFT (Intel/Micron Flash Technologies) partnership and has its own captive supply of 3D NAND, but it chose to use its planar 16nm with its 9100 Series SSDs. 

Curiously, Intel chose to sit out the latest planar NAND generation in favor of the pending IMFT 3D NAND. The new 32-layer IMFT 3D NAND has been shipping in TLC flavors for client use, but the DC P3520 marks the debut of the MLC variant, which brings more endurance than the value-optimized TLC NAND does. Intel also refreshed its enterprise SATA SSDs with its 3D MLC NAND, along with a broad spate of its consumer SSDs.

The IMFT 3D NAND brings the benefit of increased density to bear; it provides 256Gb (32GB) per die, which is double the density of the previous-generation 128Gbit 20nm NAND. Increased density reduces cost and it also brings the possibility of higher capacity SSDs, but this presented Intel with an interesting conundrum. SSD controllers, particularly for high-performance applications, require a healthy dollop of DRAM to manage the underlying pool of NAND. SSD controllers typically require 1MB of DRAM per GB of NAND, but Intel's proprietary 18-channel SSD controllers can only manage up to 2.5GB of DRAM. Intel allocates the DRAM in an ECC arrangement, so the controller only has access to 2GB of DRAM, and thus overall capacity is limited to 2TB.

Intel chose to forge ahead with its existing P Series platform instead of waiting for a more advanced controller. The P Series platform originally appeared in 2014, and the proven and mature platform is largely credited with ushering in the NVMe era in the data center. Intel's P Series brought an intense focus on performance consistency, which is a boon to real-world application performance. The DC P3520 serves as a stopgap as Intel prepares its next generation NVMe platform, but the reduced cost will give the company a more competitive stance against its surging competitors.

Specifications

The DC P3520 series only comes in three capacities (450GB, 1.2, and 2TB), which is a departure from Intel's proclivity for offering a dizzying range of capacity points. All three capacities come in both AIC (Add-In Card) and 2.5" U.2 form factors, and recommended airflow is the only differentiating feature between the two form factors. Both form factors employ the NVMe 1.0 protocol and communicate over a PCIe 3.0 x4 connection, but the U.2 models use the venerable SFF-8687 connector. Intel originally had plans to deploy a high-endurance DC P3320 variant, but it canceled the product for unknown reasons.

Density can be a double-edged sword; it lowers price, but it can also hurt performance. Intel's new 3D NAND is denser than the 20nm planar NAND it used on the DC P3500, and thus it requires fewer die to reach the same 2TB of capacity. SSDs thrive on parallelism, and the reduced number of die results in the lower random performance specifications.

The P3520 actually takes a step back on the performance front in comparison to the previous-generation DC P3500, which featured up to 430,000/28,000 read/write IOPS. The DC P3520 offers up to 375,000/26,000 random read/write IOPS, but performance varies with capacity. The DC P3520 also falls back to 1,700/1,350 MB/s of sequential read/write throughput, which is well below the 2,700/1,800 read/write throughput of the previous generation low-endurance models.

Aside from heightened density and lower cost, 3D NAND also offers more endurance due to its larger cell lithography. Intel and Micron do not disclose the actual node size, but most theorize it is in the ~3Xnm range. The increased endurance weighs in and provides the DC P3520 with up 2,490 TB of endurance, which is more than double the DC P3500's 1,095 TB.  Intel's DC P35290 features a 12W active and 4W idle power draw, which is a significant reduction compared to the DC P3500's 25W active power consumption.

Samsung and Intel are the two largest enterprise SSD vendors, and competition between the two has been stiff. Samsung has steadily gained ground in the data center over the last year and now claims to have the biggest share of the lucrative market. Much of Samsung's success has come on the back of its 3D NAND advantage, but Intel is finally firing back with its own 3D NAND products. Intel announced the new DC P3520 and a new series of dual-port NVMe DC D3700 and D3600 SSDs, which should help it regain ground in the all-flash array segment. It also has a lower-endurance DC P3320 NVMe offering that tackles the SATA segment with very low price points. Samsung also has a robust line of 3D-powered SATA SSDs that are exceedingly popular, but Intel's new DC S3520 and S3510 should help staunch the bleeding.

Samsung is also penetrating the SAS market, but Intel's position is somewhat unclear now that WD/HGST has purchased SanDisk. In the past, Intel and HGST enjoyed a collaborative partnership that spawned several successful SAS products, but with the inevitable HGST transition to SanDisk flash it appears the relationship might end on a sour note. Intel/Micron has 3D XPoint waiting in the wings, but Samsung has its own plans with its newly announced Z-NAND products.

The world of storage evolves quickly, but never more so than today, now that flash has moved to the mainstream. Let's see how Intel's latest workhorse stacks up.

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