Scale-out SSD shatters performance records

About a year ago, I wrote about the ever-decreasing role of spinning disks in highly transactional OLTP storage workloads. Back then, Texas Memory Systems had just released test results for its RamSan-630 SSD storage product that achieved more than 400,000 SPC-1 I/Os per second (IOPS) at a cost of $1.05 per I/O — a truly remarkable performance result that was (and is) impossible to achieve with traditional disks at the same price.

Today, the Storage Performance Council (SPC) published new test results for Kaminario’s K2 SSD storage product. Its record-shattering performance is in excess of 1.2 million SPC-1 IOPS for just 40 cents per I/O. That Kaminario can produce these results at such an economy is a huge testament to the advances made in SSD technology and further proof that solid state rules the roost when it comes to OLTP workloads.

[ Also on InfoWorld: See how far solid-state disks have come since Matt Prigge proclaimed them the reigning champs for storage. | Sign up for InfoWorld’s Data Explosion newsletter for news and updates on how to deal with growing volumes of data in the enterprise. ]

However, that’s not all it tells us. Although the full details aren’t yet available, it appears that Kaminario was able to more than triple Texas Memory Systems’ performance not by using an entirely new type of SSD but by using a different architecture with current SSDs. Unlike Texas Memory’s single-appliance approach or the scale-up architecture used by many traditional storage vendors, new entrants to the storage space such as Kaminario tend to develop scale-out architectures. That key difference is likely why Kaminario now holds, at least temporarily, the transaction-performance crown.

Where scale-up falls short

Although there are many variations of storage, most enterprise storage platforms fall into two groups. One starts with expensive fixed-controller resources and adds inexpensive capacity as growth is required — that’s called “scale-up.” The other relies on individual bricks of combined controller/storage resources that can be added to as performance and capacity needs dictate — that’s called “scale-out.”

Scale-up architectures have been the de facto standard in storage for the past 20 or more years. You start with a set of controllers and whatever storage resources you need immediately. As time goes on and your capacity needs increase, you simply add more and more disk resources to the architecture while the controller resource remain largely untouched.

Although convenient as you grow, this approach has some limitations. The first is that you must consider the performance and capacity requirements you expect to encounter toward the end of the architecture’s lifetime when you purchase the storage at the outset. If you don’t do this accurately, you might have to replace the controllers as your performance or capacity needs outstrip their capabilities. Given how expensive and wasteful that kind of forklift storage upgrade can be, most organizations choose to oversize the controller resources at the outset — at the cost of wasted controller resources for most of the storage system’s lifetime.

Second, scale-up architectures tend to require specialized hardware that can result in a higher overall cost. Take a typical enterprise SAN containing a few hundred disks as an example. There is no off-the-shelf hardware in existence today that can address that many disks and provide the performance as demanded by most enterprises in the market for such a SAN.

Therefore, storage vendors must design specialized controller hardware built from the ground up to serve demanding storage loads and leverage very large amounts of disk resources. And they have to develop the software to deliver the high-end functionality enterprises have come to expect, such as thin provisioning, snapshots, replication, and virtualization awareness. This all increases the cost.

Where scale-out works better — and where it doesn’t

Scale-out architectures avoid some of those pitfalls by achieving scalability through the addition of many much smaller and much cheaper chunks of storage — typically attached to industry-standard server hardware. This approach removes much of the forecasting uncertainty for the initial purchase; you often need to consider just your near-term storage requirements. As your capacity and performance outlook dictates, you can add storage resources on a pay-as-you-go basis.

Also, the ability to use largely off-the-shelf hardware components substantially decreases the hardware and development costs for the storage vendor, in turn making the storage products less expensive.

However, scale-out architectures have their downsides. Because performance and storage resources are typically linked to one another (after all, a single storage building block includes both), the ratio of performance to capacity can get out of line with an organization’s requirements, resulting in either wasted storage or wasted capacity. Many scale-out vendors try to overcome that issue by offering various models with different performance-to-capacity ratios, some using SSDs, some using SATA hard disks, and some using near-line server-attached storage. They also tier data along the storage media types as workloads dictate.

Another substantial challenge that faces scale-out vendors is how to efficiently get performance from many individual bricks of controller resources while still providing rock-solid reliability. This involves solving many of the same challenges that must be overcome in high-performance computing environments: safely and effectively parallelizing a complex and demanding workload among many compute and storage nodes while making the result appear as though it’s a single, unified architecture. That challenge places much more emphasis on the quality and innovation that goes into the software — which, in large part, is what you’re paying for.

That focus on the parallelized software is exactly what has opened the door for new scale-out storage providers such as Kaminario to carve out a niche not addressed by traditional storage architectures.

In today’s world of near-geometric data growth and ever-increasing storage loads, it’s clear that simply throwing faster and larger storage hardware at the problem isn’t the solution. The industry needs to couple those substantial gains in storage hardware capabilities with innovations in network and storage software technology — scale-out storage architectures are such a pairing.

Although not everyone is (yet) in the market for a SAN that can crank out a million IOPS, you can look to these groundbreaking storage architectures as a sign of what’s to come.

This article, “Scale-out SSD shatters performance records,” originally appeared at InfoWorld.com. Read more of Matt Prigge’s Information Overload blog and follow the latest developments in storage at InfoWorld.com. For the latest business technology news, follow InfoWorld.com on Twitter.