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Facebook storage wish list calls for faster flash innovation

Facebook's strategy for flash storage technology revolves around disaggregation, tiers and innovating in emerging tech, such as NVMe, QLC and 3D XPoint.

SANTA CLARA, Calif. -- Facebook, one of the most innovative and largest consumers of flash storage, presented the...

industry with its wish list on the opening day of the Flash Memory Summit.

"There are four asks we have of this industry," Vijay Rao, Facebook's director of technology and strategy, said during his FMS keynote Tuesday.

Rao's Facebook storage requests were for standardization of the nonvolatile memory express (NVMe) protocol; more innovative, next-generation NVMe products; quad-level cell (QLC) flash; and more M.2 products. All of these are already in the works, and Facebook has asked for several before. Rao pointed out this is not Facebook's first request for QLC, and it also called for the smaller M.2 solid-state drive form factor in 2014.

QLC stores four bits per cell, compared with the still-emerging triple-level cell flash that stores three bits per cell.

Rao also said a surprising Facebook storage request from 2014 -- Blu-ray optical disks for cold storage -- remains part of the social media giant's storage strategy.

"We asked for QLC flash a few years ago, and we ask for it again," Rao said. "We are rooting for our partners to have QLC NAND for high density in production soon."

"We're constantly looking for ways to grow our infrastructure to make it more efficient," Rao said.

Facebook isn't sitting around and waiting for vendors to deliver its wish list in commercial products. Rao spoke of several homegrown flash storage products Facebook has already built for testing, as it tries to keep up with billions of users, frequent spikes during holidays and breaking news events that send people to its pages. Rao said Facebook's compute power is about 7.5 quadrillion instructions per second.

"It puts a lot of stress on our infrastructure," he said. "But that's what makes it fun."

Rao talked in detail about Lightning, Facebook's internally created NVMe JBOF, or just a bunch of flash, box first revealed at the Open Compute Project Summit in March. Lightning supports several SSD form factors, including M.2, as well as standard 2.5-inch and 3.5-inch drives. It supports four head nodes per tray, allowing different types of storage and the ability to adjust the compute-to-storage ratio.

Rao called Lightning part of Facebook storage's "disaggregated rack challenge. It allows resources to scale independently." He said the strategy improved Facebook's storage and server performance by 40%.

We're constantly looking for ways to grow our infrastructure to make it more efficient.
Vijay Raodirector of technology and strategy, Facebook

Rao also discussed Facebook's AVA card that contains four M.2 NVMe modules to increase density and lower power consumption. He said Facebook is also experimenting with 3D XPoint, which is "significantly faster than NAND, but requires us to make significant internal modifications." Facebook developers have tripled the performance of early Intel Optane 3D XPoint SSDs and reduced latency to one-tenth of its previous rate, Rao said.

Facebook storage is also experimenting with WORM, or write once read many, flash storage that holds 100 TB of capacity and low endurance -- 150 write cycles -- for cold storage.

"For applications where hard disks are too low performance and flash is too high performance, we use WORM," Rao said. "We're looking at Blu-ray for high capacity."

Of course, Facebook isn't your typical enterprise storage shop, as another presenter pointed out.

"The difference between Facebook and most data centers is Facebook has 4 billion people accessing hot data and 4 million people accessing cold data," said Howard Marks, founder of consultant firm DeepStorage, during a session on enterprise flash storage technologies.

"And Facebook's cold data is 100 degrees Celsius."

Still, storage vendors at the summit said they are happy to accommodate Facebook's storage needs. "I have the answer for his asks," said Micron Technology's storage vice president, Darren Thomas, who delivered the keynote following Rao. Thomas unveiled Micron's QuantX brand for 3D XPoint, which is the vendor's answer to Intel's Optane.

Steve Garceau, Toshiba's manager of enterprise SSD marketing, said the vendor expects 3D XPoint products by 2018.

In the meantime, Toshiba showed off its Flashmatrix data analytics array that packs 384 GB of DRAM and 24 flash storage drives into a 2U enclosure.

For pure capacity freaks, Seagate demonstrated a 60 TB 3.5-inch SAS SSD that uses Micron 3D NAND. Seagate expects the 60 TB whopper to ship by the end of 2016.

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