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Editor:- February 4, 2014 - PLX today announced it is the 1st PCIe switch vendor to have achieved Gen3 compliance having passed the compliance testing procedures of PCI-SIG.
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PCIe SSDs and storage interface glue chips

PCIe chips from PLX - click for more info
switches for leading PCIe SSD designs
ExpressLane™ from PLX Technology
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find out more about PCIe chips and their possible uses in SSDs
by Zsolt Kerekes, editor

PCIe SSD market - the first 6½ years

StorageSearch.com has focused on enterprise SSDs since the 1990s - and our readers were at the forefront of the PCIe SSD market - since the first enterprise PCIe SSD products came to the open market in 2007.

At that time some people were asking - how would PCIe SSDs fit into the enterprise SSD market landscape? - which was dominated at the top end by proprietary rackmount systems - and a small number of fibre-channel 3.5" SSD drives. Most SSD market experts at that time - didn't think PCIe SSDs would stick - except as a small niche. Instead the "safe" money was on predictable incremental changes - which were then already in progress. The hard drive way of thinking was that the enterprise DAS SSD market would evolve with 3.5" giving way to 2.5" form factors and SATA giving way to SAS. And if servers needed access to larger amounts of fast SSD capacity this could be easily implemented by classic arrays of these smaller drives. SSDs were just replacements for HDDs - weren't they?

That's not the way the thought leaders in the SSD market saw it, however.

The number of PCIe SSD vendors kept growing - and the products kept getting faster and better. So much so that in September 2009 - I announced that StorageSearch.com searches for "PCIe SSDs" and related technology content had overtaken searches for 2.5" SSDs - marking a decisive turning point in the direction the SSD market was taking.

Today the importance and size of the SSD market and the significance of PCIe SSDs as a distinct and permanent feature of enterprise architecture have become clear to all.

With over 100 million enterprise PCIe ports already shipped in the market (as of January 2014) and with waiting-to-be-exploited fabric capabilities which chipmaker PLX calls "ExpressFabric" (by which they mean PCIe as a fabric outside the box but still within the cabinet) the converging PCIe SSD / server has already been a fast changing market and is well positioned to expand into new applications.

You might think that 7 years after the first PCIe SSD cards were being designed - it would be about time for the rate of change in this technology to slow down a bit. But far from it. New controller technologies and architectures have been designed to span multiple memory generations, technology generations and even memory types. And in 2013 we started seeing more new features and form factors for PCIe SSDs.

PCIe SSDs are now at the forefront of all high performance enterprise SSD design.

PCIe has become the incubator for testing new SSD concepts and getting them to market quickly. Whether it's a new memory architecture, a new non volatile memory type, a new reliability feature or a new way of connecting clusters of servers to arrays of SSDs - this is the market where the exciting hot ideas are seen first.

There are many reasons you might want to learn more about PCIe interface technology and the glue chips and IP from the world's leading supplier PLX (70% PCIe switch market share).
  • SSD designers - if you're designing a PCIe SSD for the first time - you might want to see the educational materials that PLX has developed for the SSD market. The world's leading PCIe SSD companies already use their chips - but for newcomers it's now easier to dive into this technology -with tech support and even a system design kit.
  • SSD marketers - you need to have an outline of what PCIe interconect technology can do now - and also have a preview of new features which you can leverage with your planned memory and controller roadmaps.
  • SSD system architects - if you know the roadmap for PCIe's capabilities- with respect to latency, throughput, topologies, fail-over and clustering - you will be better placed to evaluate new products which you read about and decide where they fit - compared with anticipated "best of breed" products which haven't been launched yet.
  • end users, investors and general readers - you don't need to know how these chips work - but it's interesting to see how PCIe supports ways of connecting SSDs (to servers and to each other) which are sometimes similar and other times different to what you might expect from just knowing about other storage interfaces and networks. And knowing more about the possibilities enabled by PCIe technology will help you get a better feel for how it compares to the other options you already know about.
I confess - that for many years - like most of you - I didn't read too much about about PCIe chips beyond the headline capabilities of what each generation could achieve in terms of raw throughput.

My thinking was - isn't the idea of standards to ensure that all these things can connect to each other and work in the same way? (Interoperability.) I guess that's one view. But most memory chips have standards too. And if you look at all the diversity in SSDs which have been enabled by different architectures and different memory management schemes - you'll realize that standards merely define the lowest common denominator of what can be done.

enter the fast lane to the future of PCIe SSDs

The art of "what is possible in SSD design" - by using so-called standard components in new ways - which is different for each chip vendor - is constrained only by the imagination, market economics and physics. If you understand more about what PCIe chips can do in SSD designs you'll be in the fast lane towards the exciting decades long journey to the solid state storage future.
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editor's summary of key PCIe / SSD articles, links and videos from PLX Technology

raw links to product data and resources
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Enabling PCIe SSDs - a PCIe chipmaker's view - this article introduces you to what PCIe can do for SSDs. It has some nice pictures which show you some of the various connection architectures that PLX's chips support. ... click to read the article in CTR magazine

extract - "In its first generation, referred to as Gen1, the speed was set at 2.5 giga-transfers per second (GT/s) serial bi-directional interface, then later enhanced to 5GT/s (Gen2) and eventually 8GT/s (Gen3). The PCI-SIG forum is already discussing 16GT/s for Gen4. The beauty of PCIe is that a designer can combine 2, 4, 8 or 16 of these PCIe lanes into a single data port. Equally important to those designers is that all PCIe Gen2 and Gen3 ports are required to be backward-compatible."
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PCIe in enterprise SSD designs (video) - this includes an introductory tutorial into PCIe and its performance and architectural capabilities for SSDs including automatic failover and multi-host capabilities. PLX's switch chips also supports failover if the fault occurs in the PCIe switch fabric chips themselves. ... click to watch the PCIe in SSD video

extract - "...And in case one of the hosts fails and you want to connect the SSDs - or the devices connected to that host - to another host - that can be done automatically as well - and the surviving host can attach the devices that were attached to the failing host to itself and control it so that the system doesn't go down and the data stored in these devices doesn't get isolated from the main system."
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PCIe as a fabric for data center clustering (video) - PLX's PCIe extenders and switch chips support lossless, software light, high performance CPU to CPU memory transfers - and shared I/O - for upto about 200 nodes - as a mini-cluster. At the next level of scalability you can interconnect these clusters. ... PCIe clustering and failover video

extract - "The host to host communication can take place directly between CPU to CPU through the PCI express fabric or through a shared neck. ...For latency critical apps you can pretty much do memory to memory transfers and writes using the PCIe fabric. The PCIe extenders are very low cost, very low power, high performance. And the PCIe fabric itself supports full peer to peer functionality. So on a 48 lane switch in Gen3 you have 96 gigabytes per second of performance that's available to you."
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Editor:- July 17, 2013 - Taking PCIe Out of the Box - is just one of the many different topologies discussed in a new white paper about PCIe and enterprise storage from PLX called - Enterprise Storage and PCI Express
image from PLX article about PCIe SSD topologies

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PCIe as a fabric image - click for more info
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