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All-flash storage arrays look set to become cheaper than magnetic media in Australia and New Zealand this year – at least for some applications
According to John Martin, principal technologist at NetApp ANZ, growth in AFAs in Australia is strong. “Overall, the hybrid market is still about 10 times the size of the all-flash market, but all-flash sales are growing almost five times as fast as hybrid,” he says.
But what exactly are all-flash arrays (AFAs), and why are they becoming more popular? What are their pros and cons for data storage?
Even the term itself is a tricky one. John Monroe, research vice-president of datacentre systems, technology and service provider research at Gartner, says: “Please note our definition for SSAs [solid-state arrays], and note that we deliberately did not choose to use the AFA term, because the underlying media may (or may not) be flash in the future (but some other form of non-volatile semiconductor media), and there are other solid-state media technologies integrated in SSAs that are currently shipping.”
AFA is a term used by many manufacturers, so we’ll stick with it here. But let’s look at the background. Once upon a time – it seems like a lifetime ago, but was only a decade or so – storage was magnetic. Whether you were running a corporate server farm or an archiving system, your medium of choice was either spinning magnetic disks or, for some specialist applications, cartridges of magnetic tape.
In the intervening years, solid-state disks (SSDs) have become more popular in laptops and desktop machines because of their speed and resistance to physical damage. However, pricing and other concerns kept such drives out of the corporate storage arena for a long time. Even when they did make an appearance, they were mainly used as caches for time-sensitive data. Bulk storage was still on spinning disks.
Price has continued to be the sticking point. It’s been much cheaper to manufacture a spinning magnetic disk than the equivalent amount of Nand flash memory for SSDs. Areal densities (the amount of data that can be stored on a magnetic disk platter) have increased roughly in line with Moore’s Law. Whatever the SSD makers have done, the magnetic disk makers (often a separate division within the same company) have kept one step ahead.
This has led to a situation where a large storage server array will usually consist of a small proportion of SSDs sit- ting “on top” of a rack of spinning disks. The SSDs provide fast read/write access to data, which is intelligently copied to/from the magnetic disks as required.
It works, producing surprisingly fast access to data. In fact, such hybrid configurations have even found their way back into desktop machines, with combined SSD/magnetic drives available for home and office users.
But now something new is happening. Magnetic disk drive capacity increases are slowing compared to the gains made by Nand. You can still buy bigger physical hard drives each year, but the difference isn’t as great as it once was. The trials of squeezing ever more data into the same area are becoming harder to overcome. The magnetic dipoles involved are so small now that quantum effects govern the efficiency of the read/write processes.
While this has been going on, Nand capacities have been growing apace. More importantly, costs have been dropping – fast. It looks as though the transition point for some applications might occur this year. That is, Nand drives will be cheaper in some circumstances than conventional spinning magnetic disks. Which brings us to the era of AFAs: servers packed with Nand drives only – not a spinning disk in sight.
This isn’t something that’s only happening in far-away parts of the world. It’s happening now, in ANZ. Earlier this year, Dell announced its Storage SC4020 Entry- Level AFA single-tier configuration, with prices starting at under AU$30,000. That money gets you six 480GB read-intensive SSDs, totalling 2.8TB. Alan Atkinson, general manager at Dell Storage, says: “For years, price has been the number one barrier to enterprise flash adoption, and we’re knocking down these walls to make the high performance, reliability and smaller footprint of flash practical for almost any workload.”
Note the “read-intensive” part of the product description. Nand drives behave in different ways, and can be optimised for either read or write operations. This is different to magnetic media, where fast read performance is usually – though not always – accompanied by fast write performance. Anyone developing storage systems based on AFAs will have to take these differences into account. It’s not a huge problem, since reads and writes can be directed to different top-layer devices, but it’s still a consideration. Increasingly, this is taken care of by software or firmware in the storage devices themselves.
Other companies are offering AFA products too, and have been for some time. NetApp, which has a strong presence in ANZ, offers them alongside its hybrid storage offerings. So does EMC, another big supplier to this market. In fact, it’s common to find hybrid systems being offered alongside all-flash ones. According to NetApp ANZ’s Martin, the growth in hybrid hasn’t really stopped in the face of all-flash arrays. “It seems that all-flash is having more of an impact on the high end of the market for the traditional ‘Tier-1’ Frame arrays which has seen a significant slowdown over the past couple of years,” he says.
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Gartner’s Monroe agrees that conventional spinning disks won’t be disappearing soon. “The rumours of HDD ‘demise’ partake of a stupefying quantity of hype,” he says.
It’s hard to get exact figures for this market to see what’s happening on the ground. Gartner’s data shows that Asia-Pacific as a whole accounted for 8% of global AFA shipments in 2014, but it doesn’t have figures specifically for ANZ. “Because the market is so nascent, we don’t have further regional breakdowns,” says Monroe. Still, it’s clear that demand for AFAs in ANZ is growing.
Flash memory does have some drawbacks, though not as many as you might expect. For example, there’s a widespread belief that, compared with conventional disk storage, flash offers fewer write cycles. But wear-levelling firmware, which ensures that all areas of the “disk” are used equally, is prolonging lifetimes for Nand devices.
According to NetApp ANZ’s Martin, flash wear is not an issue worth considering. “I could write a book about how much of a non-issue it is, lots of concern with no real justification,” he says.
Flash drives are also quieter than magnetic drives, since there are no moving parts. They consume less energy, for the same reason – they don’t have to spin platters or move read-write heads thousands of times per second. And because they consume less energy they also emit less energy, so flash drives run cooler than most spinning disk drives, which has another knock-on benefit – the air conditioning electricity bill for your datacentre just got cheaper. All of this must be taken into account when comparing prices between Nand and magnetic drives.
But what really matters is the performance. Flash memory leaves magnetic media trailing in its wake when it comes to access-intensive applications. An optimised SSD can be an order of magnitude faster for read operations. An organisation moving from conventional storage to AFA devices might notice such a significant performance increase that the bottleneck in their system is no longer the storage device. From being storage-constrained to becoming processor-constrained can be quite a surprise – and a welcome one.
We’re not quite at the stage where magnetic media is redundant. Alongside its AFA announcement, Dell launched a flash-optimised storage product for ANZ, which combines flash devices with conventional spinning disks. Other major storage device suppliers continue to sell high volumes of hybrid data storage systems too. As Gartner’s Monroe puts it, “HDD-based, hybrid HDD-/SSD-based and SSD-based systems will reflect a symbiotic evolution.” Hybrid is the configuration that continues to offer the best of both worlds – price and performance. At least, it does for now. Just maybe not for much longer.
NetApp ANZ’s Martin says: “I’d expect the all-flash market to accelerate in ANZ and, given how quick this part of the world is in adopting new technology, I’d expect ANZ to become one of the world’s most successful adopters of all-flash-arrays – until the next big disruption comes along (probably sometime around 2020).”
ALEX CRUICKSHANK has been a technology journalist since 1994. He grew up in the UK and now lives in New Zealand, where he runs his own writing business.