All-flash storage arrays: Are they killing hybrids?

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This article is part of our Essential Guide: Flash options for the array or server

Flash-only arrays replacing hybrids for primary storage

With a bevy of all-flash arrays coming out in early 2016, flash is becoming the only game in town for primary storage. Hard disk drives are being relegated to cold storage.

Judging by the recent flood of flash-only storage launches, you can expect to soon see the primary storage hybrid array on the endangered species list -- right alongside the black rhino and blue whale.

Almost all of the new primary storage launches these days are all-flash arrays. Since the start of 2016, EMC, Hitachi Data Systems, Pure Storage, Nimble Storage, Tegile, IBM and X-IO Technologies have launched flash-only primary storage arrays. That doesn't count NetApp's acquisition of SolidFire's all-flash platform. Most of the large storage vendors have several all-flash products, and it's become difficult to find a storage array vendor without any flash-only platforms.

Of course, storage and IT technologies die hard. Tape and mainframe are exhibits A and B of that. But recent product launches make you think the entire world is going all-flash. And it is, for primary storage. The fastest hard disk drives are already disappearing from primary storage arrays. It will probably take at least a few years, but it's more a question of when than if HDDs will disappear from arrays, except for bulk storage.

Flash proponents said that day is closer than you think.

There is no longer any reason for customers to purchase disk solutions.
Scott DietzenCEO of Pure Storage

"There is no longer any reason for customers to purchase disk solutions," Scott Dietzen, CEO of all-flash specialist Pure Storage, said of the recent gush of all-flash arrays.

EMC declared 2016 the year of all-flash for primary storage, while launching two flash-only systems in February. That's after selling $1 billion worth of all-flash XtremIO arrays in 2015. Other legacy vendors agree with EMC's proclamation.

"Now that pretty much every vendor, large and small, has all-flash arrays in the market, that's the end of the all-flash array as this special thing. It's just primary storage now," said Dave Wright, NetApp vice president, and SolidFire's founder and former CEO. "I don't think disk is going away any time soon, but it's more and more being relegated toward cold storage, secondary storage, backup, archive [and] object storage."

As flash prices decline and users encounter more applications that require high performance, solid-state drives are replacing 15,000 RPM HDDs inside of storage arrays. HDDs are being relegated to cloud providers and on-premises bulk storage.

Users drawn to flash

Performance-hungry users find less need for hard drives after they get a taste of SSDs.

"I haven't talked to one end user [who] has deployed flash that doesn't want more," said Eric Burgener, storage research director for market research firm IDC. "Flash is better on performance and reliability, uses less power, and has better CPU utilization."

Health Network Laboratories in Allentown, Pa., is a prime example of that. HNL initially bought XtremIO specifically for virtual desktops. Less than a year later, CIO Harvey Guindi said he plans to purchase all-flash for his primary storage.

"We have already made the determination that all new storage growth is going to be flash," Guindi said.

Guindi said he will move high-performance Microsoft SQL Server database workloads that stress performance of his EMC VNX hybrid arrays to XtremIO. "We think we're just going to keep adding XtremIO for high performance and expand VNX with flash, but more for things that don't demand as much performance," he said.

Flash proponents claimed long-term total cost of ownership (TCO) for all-SSD arrays is roughly the same as for hybrids. That TCO includes the price of power, maintenance, space and other factors.

"TCO is already compelling for flash," IDC's Burgener said. "You can buy 20 SSDs to do the work of 250 hard disk drives. But you couldn't buy into a flash array for as low a price as you can buy a hard-disk array."

Bill Evans, vice president of IT at Ferrellgas, based in Overland Park, Kan., said he didn't consider all-flash feasible when he started looking for a new storage array in early 2015. He ended up buying four Violin Memory Flash Storage Platform 7300 all-flash arrays, which he said cost less than the hybrid options he looked at from EMC and IBM for the same performance. Ferrellgas is moving its SQL Server databases to the Violin systems, and Evans is in the flash-only camp for primary storage.

"When we started our evaluation, we had no idea we could afford an all-flash array," Evans said. "Flash had been pretty darn expensive. We had a little bit before, and used it carefully. It was a challenge trying to manage that. Going to all-flash took away the extra management of putting data in the right places on our storage. And we've seen considerable performance improvements."

Not everybody finds SSDs to be a bargain, though. If flash cost the same as disk drives, all-flash storage would already have taken over the world. Even with the cost of flash coming down, with advances such as TLC 3D NAND, the entry price still remains an issue for many.

The raw cost of flash is still higher than HDDs, even if you figure in data reduction for flash. SSDs cost around $8 to $9 per GB compared with about $0.35 per GB for the most expensive HDDs.

According to TechTarget Research's Q4 2015 post-purchase survey for all-flash arrays, the average selling price for a flash-only array was $1.63 million for 63 deals in the quarter.

Michael Scarpelli, IT director for the La Jolla Institute for Allergy & Immunology in La Jolla, Calif., uses hybrid arrays from Nimble Storage and Reduxio, and takes advantage of flash's performance for virtual machine storage. But he said the idea of all-flash for all primary storage remains beyond his budget.

"The limiting factor for us is cost," Scarpelli said. "If I had my druthers, sure, I'd go all-flash. Why not? But when we're going for storage, we basically drop in what is going to be the cheapest and most reliable drives. When we're dealing with VM-related storage, we always try to get a little of that flash in there, because you want that fast. You want fast writes, fast reads, fast cache. We usually want some of it, but if a product did not have that, I don't know that would turn me off."

Hybrid infrastructure will outlive hybrid arrays

Mark Peters, a senior analyst at Enterprise Strategy Group Inc., in Milford, Mass., said the recent flash-only flood "is testimony that we are in the midst of a media change across the whole market. As price drops and flash become more accessible, it's logical that it will take over for disk." Still, he said a role remains for HDDs, whether they are inside primary arrays or not.

"I am still a massive fan of hybrid, with the word infrastructure behind it rather than array," Peters said. "The need for hybrid is absolute, unless you want to waste money. Why would you put cold data on flash? It's not sensible."

Even if all primary workloads go to flash, Peters said HDDs will play an important role in storage for a long time. "The TCO of flash is becoming attractive at the high end, because you were going to pay more anyway," he said. "At that high end, I agree, flash makes sense. But for data you are going to use only occasionally, it makes sense to consider disk."

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