On many fronts, hard-disk drives are losing ground to faster and more efficient flash-based drives.
The struggle for market share between flash-based drives and hard-disk drives is so similar to physical conflict that we can apply the same language. Wars are essentially territorial, with outcomes determined by who owns the battlefield. Logistics chains and technological leadership often determine point battles and having superiority of resources is always a major factor in sustaining an attack.
We often see the flash/HDD battle portrayed as a cloudy whole, forgetting that there are in fact a series of battlefronts. The devil is in the details and a map of the storage world today shows how, insidiously, flash-based products have gained almost all the available territory.
Storage today ranges from small drives used in medical and industrial gear to super-fast all-flash arrays that deliver millions of I/O operations per second. Factors such as weight, physical size, and power help determine the best storage match, together with price and performance. Logistics -- for example, the availability of component die -- are a major factor in setting storage prices and thus the balance of competitiveness.
To complicate issues, however, flash and HDDs are miles apart when it comes to performance. Using a solid-state drive may make a server run three or more times faster than the same configuration using HDDs. This is the technology component of the battlefront. Many comparisons of HDD and SSD prices ignore the impact of the difference on overall TCO, so consequently they overstate the cost of SSD-based solutions. This oversight has slowed SSD sales for years, though the industry today has mostly savvied up.
As we fly over the storage drive battlefields, what do we see? SSDs have established total technological dominance in most areas. For example, 15K and 10K RPM hard drives are topped out and starved of future investment; they just can’t keep up with SSDs and they cost more. This concedes the enterprise drive space to SSDs, with a resulting decline in RAID arrays and SAN gear. It’s interesting that SANs aren’t surrendering yet, but I’ll touch on that later.
The mobile PC space faces a race to the bottom, which has forced vendors to enrich configurations to make any margin. An obvious play is to go all-flash, implying longer battery life and less weight, among other benefits. SSDs now own most of this territory.
As we go territory by territory, we see that flash has won or is winning handily. The one exception is nearline bulk storage, where top hard-disk drive vendor Seagate, projects 10 more years of HDD dominance in bulk storage. I don’t buy that story and you'll see why in this slideshow!
Note that battles may be won, but storage is a conservative market and change takes years. Businesses are still buying 15 K hard drives and nearline SATA drives won’t go away overnight!
Cameras, phones, tablets, and IoT
Attempts to make one-inch hard drives for the handheld markets crashed and burned with the realization that you couldn’t make them cheap enough to win. Weight, power use, and a lack of shock resistance all added nails to the coffin. This made solid-state storage the only viable path, but solid state added the ability to right-size the memory to the job, giving us drives with 16, 32 and 64GB, all of which would have been the same 512GB drive in the HDD space.
This vast and fertile territory of handheld devices and the internet of things is the genesis of flash domination, paving the way for lower prices in the computer space.
Historically, laptops used HDDs, in a price-dominated market. PC demand has dropped in the last two years, leading to a race to the bottom on prices for entry-level units. To restore margin, vendors have migrated to a richer offering, with slimmer and lighter designs and longer battery life. Getting there meant a switch to SSDs, which has moved SSDs closer to the dominant role in laptop storage.
Continuing decline in the mobile segment guarantees that SSDs will take over, especially given the ability to use 256 and 512GB drives to lower costs, as opposed to the minimum 1TB of HDDS. Most users don’t need 1TB on their laptop.
Dominance of this segment by 15K RPM HDDs is in the past. Consumer SSDs are much faster and, with newly released software from all the major vendors that allows the storage admin to trade capacity for wear-life, they can achieve substantial operating lives.
Consumer-class drives boost performance way past HDDs. The resulting reduction in the number of servers for any given workload offsets the price of the drives, while use of top-end SSDs can boost performance much higher still.
Viewed from a total-cost-of-ownership level, SSDs are an excellent investment for server farms. The result is the demise of the 15K and 10K RPM HDDs in the server market.
With many slow drives attached to a network connection, RAID arrays and SANs took a real hit when SSDs arrived on the market. Typically, four SSDs could saturate the I/O on a RAID array, creating a serious mismatch in performance. Adding to the woes, all-flash arrays arrived as a turbo-booster to any SAN.
RAID arrays are being relegated to secondary storage, along with SATA nearline drives. These drives are the only segment of the HDD business showing growth today due to the adoption of storage tiering, though RAID array sales are declining. Nearline drives are higher priced than commodity HDDs due to the need to protect against rotational vibration. This forces RAID arrays to use robust and expensive metal work.
RAID arrays are competing against appliances designed from scratch to match SSD needs, with faster host connections, RDMA link control, and inexpensive packaging. SSDs are typically 2.5” form factor, making for a compact appliance.
The final battle
The price advantage of hard-disk drives is eroding. New SSD technology allows massive die stacking, while QLC cell technology will add 40% to drive capacity. Even small drives will exceed the best that a hard drive can do. We are seeing 32TB and larger already on the market, with 64TB or more expected in 2019.
HDD is stuck in a rut. Capacities of 18TB are just now shipping, but capacity growth is hampered by delays in a radical new technology, HAMR recording. Even with HAMR, HDD density improvement still will be slow. HDD is losing the battle with no way to catch up.
But there’s more: Hard-disk drive rebuild times are horrendously long and 20TB drives create risks. That may be why the sweet spot in HDD sales is still 4TB.
With Samsung and Intel planning ruler-sized SSDs, we’ll see a petabyte in a 1U appliance. Other compact form factors exist. These make downsizing appliances very feasible, while high SSD capacities reduce the appliance count and offset the cost of the SSDs.
Given the SSD advantage, it’s just a matter of time -- and foundry capacity -- before HDDs lose this final battle.