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an introduction to enterprise SSD silos

7 ways to classify where all SSDs will fit in the pure SSD datacenter

by Zsolt Kerekes, editor - March 27, 2012

I get many questions asking me to explain how the various pieces of my enterprise SSD market model and architecture models fit together to help them understand some basic questions like this...
  • what are the main types of SSDs that we'll see in the future enterprise SSD market?
  • which companies are the likely leaders in these future segments?
  • is SSD company X - a leader or a future drop out?
  • how much is this company / technology / market segment - really worth? - and for how long.
  • do these companies X and Y really compete with each other? - if one wins - does that mean all the others lose?
  • if I bought this SSD company - would it be worthwhile?
You can see how this goes...

The purpose of this new article is to provide a top level summary of the smallest number of usefully different types of SSD system which can coexist sustainably and inter-operate in distinctly different roles in the architecture of the pure solid state enterprise datacenter of the future.

Most of the interface types and form factors and memory types for SSDs have been around in some form for many years. This isn't about morphology. Although shape and interface type do come into the scope of the classifications below - when they are relevant.

SSD application silos within enterprise architecture

When thinking about where SSD products fit into the pure solid state storage enterprise datacenter architecture it can be useful to think about them from the point of view of application silos - and where they sit relative to the application processors.

Vendors - who by design (or accident) - offer products which match the specification and price contours of these SSD silos - will have advantages over competitors whose products don't.

SSDs aren't islands - their data always comes from and goes on to other SSDs

Enterprise SSDs which have been designed without any reference to how they will segment and interact with other types of SSDs - in the mind's eye of the customer architecture - will eventually fail in the market - because they will have the wrong set of technical features and therefore cost more to satisfy the genuine SSD architecture needs of the market.

An example here would be a "fast SSD rack" designed for apps acceleration - but which also included dedupe and compression. These are inappropriate features for this class of product.

Such a product set may work for some customers - but mismatched feature sets are not scalable over time and over bigger markets.

The enterprise SSD market is complicated enough already and users will steer towards a simple set of standard product types which meet universal needs and which can be almost seamlessly replaced by similar products from competing vendors - without re-engineering the user's legacy SSD architecture.

All server SSDs can be described as fitting into one or more of the following categories.
  • PCIe SSD cards / modules (or whatever replaces PCIe in the future as a generally available lowest latency, highest bandwidth connection between SSD memory arrays and server CPUs - such as memory channel SSDs ).

    App silo = acceleration SSD (internal).

    Lives closest to the application server (and often inside the server box)

    Why do people buy them? Because they provide easy to understand, easy to scale and low cost ways to increase virtual server apps performance - by placing useful amounts of low latency storage transparently close to the CPU.

    Not all PCIe SSDs are the same. The PCIe SSD market will, itself fragment into about many different types. ultrafast, fast, fast enough, ASAP, legacy vs new dynasty, and standard reliability vs high availability. And the PCIe attachment concept is also stretching into the popular removable 2.5" form factor too.

    Examples of companies who offer products in this form factor include:- Fusion-io, Texas Memory Systems, Virident Systems, OCZ and LSI. About 30 other companies are listed in the PCIe SSDs directory.
  • ultrafast rackmount SSDs. In today's market the fastest rackmount SSDs on the SAN are always RAM SSDs. So I was tempted to just label this category "RAM SSDs" - but that would be misleading because RAM SSDs are available in other form factors too - such as 3.5" and PCIe cards - so that wouldn't be so clear.

    Whatever the memory technology - the ultrafast rackmount SSDs provide ultimate low latency and the highest random IOPS for any size of blocks.

    App silo = acceleration SSD (on the SAN).

    Why do people buy them? (Given that they are the highest cost storage per terabyte and lowest density per rack unit)...

    RAM SSDs solve some bottleneck problems which are either impossible to solve with other SSD technologies - or which would cost much more by requiring more servers combined with over-provisioning of fast flash SSDs for example.

    Examples of companies in this category include:- Kove, Kaminario and Texas Memory Systems.
  • fast rackmount SSDs. In today's market these are the fastest flash SSD systems which you see from companies like Texas Memory Systems and Violin. Their primary characteristic is speed. And they connect via traditional storage networks like FC SAN , iSCSI, IB and even PCIe.

    App silo = acceleration SSD (on the SAN).

    Why do people buy them? - To get very high performance. But most enterprises don't need this level of performance and even enterpirises which can benefit from these fast systems can't afford to implement all their SSD storage exclusively with these fast SSDs. That's why there's another distinct type below.
  • fast enough rackmount SSDs. These are SSD arrays which are 5x to 10x slower than the fastest "fast SSD racks" in the same memory technology.

    App silo here depends on the enterprise. It can be viewed either as the main form of acceleration SSD on the SAN (in situations which don't need the faster SSDs) or it can be viewed as a distinctly different SSD performance layer on the SAN (auxilary acceleration SAN SSD).

    So why would anyone buy them? Because they're significantly cheaper - for the same capacity. They're cheaper - because they are much easier to design than the fast systems.

    Fast-enough SSD racks still provide useful speedups compared to legacy HDD arrays, and are faster than bulk storage SSDs (below). For many types of apps - this is as fast as the rackmount SSD has to go. Faster operation would be economic overkill for the business. Like all rackmount SSDs - they can co-exist in the same enterprise with PCIe SSDs (which are essentially part of the server).

    Examples of companies in this category include Texas Memory Systems and Violin who have diversified their product lines to offer cheaper / slower models. It also includes companies like WhipTail Technologies, Nimbus Data Systems and Pure Storage.
  • capacity maximized SSD racks / bulk storage SSDs / archive SSDs / cloud storage SSDs.

    These systems provide the maximum amount of SSD capacity per rack unit at the lowest operating cost (and lowest electrical power). But their latency and random IOPS is orders of magnitude slower than fast SSD rack systems.

    So why would anyone buy them? Because they provide the lowest cost usable storage on the planet (even lower cost than HDD arrays). The main applications are backup and archival storage.

    A typical feature of this type of SSD system is transparent integrated compression and deduplication. In other types of SSD rack that would compromize performance - but in these systems capacity density has the highest design rating.

    Vendors in this category include:- GreenBytes and Skyera.
  • SSD ASAPs (auto accelerating / caching / tiering SSDs). The main role of these storage appliances is to intermediate between the top levels of installed SSD speed in the enterprise.

    Why would anyone buy them? - No single SSD type can match all the needs of all user enterprises economically. And there will always be a need to have intermediate management between SSD systems which have dissimilar speed / cost characteristics.
  • high availability / fault tolerant SSDs. Unlike standard SSD systems - which may have some fault tolerant aspects in their design such as RAID - the HA SSDs include significant features in their designs which support performance while offering no single point of failure. Performance - and in particular latency - is not significantly degraded in the event of sub systems failure. That's in contrast to other methods which wrap failover support outside the SSD box - and can destroy the performance advantages of the SSD when it's in safely failed mode.

    HA SSDs can be classified as fast or fast enough.

    App silo = acceleration SSD (on the SAN).

    In the current market there's no point in vendors offering HA SSDs with lower performance - such as for archiving. Bulk storage SSDs will have replication features already built-in - as it's relatively cheap to achieve this using traditional methods which are already compatible with the slow latencies offered by such systems.

This is where the 7 distinct enterprise SSD silos list ends. It's only if you're being really picky about completeness - that you might also want to find a place for 2 other categories below - which aren't really part of the SSD app silo model.
  • component SSDs. This isn't a new classification. But obviously most of the above rackmount SSD types for example can be implemented internally by arrays of smaller SSD modules such as 1.8" SSDs, 2.5" SSDs and even PCIe SSDs. These SSD components can be used inside what I call "open" or COTS (commercial off the shelf) SSD arrays - which can be engineered to meet any of the above purposes.

    From the marketing point of view there are already many long established and useful ways to segment the SSD components sub-markets - such as form factor, interface, data integrity, security, industrial, military, notebook, enterprise etc - such as in our SSD buyers guides.

    There's an overlap between SSD vendors who market SSD systems and those which only market components for so called oem use - (use by other manufacturers). From the user's point of view these differences of sourcing are most apparent in the "fast SSD rack" category - and least visible in the "fast enough SSD rack category". These differences to do with SSD controller design and big versus small SSD architecture - have been dicussed in other articles - so I won't repeat them here.
  • notebook SSDs - It doesn't add anything to our understanding to include notebook SSDs within this classification article.

    Do PCs, notebooks, netbooks, tablets, phones etc form part of the enterprise SSD population?

    Yes of course they do - because most of the demand seen in the application servers originates from people using (for want of a better word) PCs. But from the marketing point of view the segmentation of SSDs within these devices is best dealt with at the component level. And there are plenty of SSD analysts who can tell you anything you can afford to know about the SSD notebook market.

    Enterprise buyers don't choose their notebooks because of how well their internal SSDs interact with their server SSDs. The choice of notebook SSD is irrelevant to the datacenter architect. Instead it's the pattern of the total data demand originated from all the notebooks which is the key factor. There's a disconnect when we get to this level.
And that seems like a good place to finally end these notes.

For more related enterprise SSD articles - take a look at the list I picked in the right hand side of this page - or for other recent SSD blogs see the index page (home page) of or take a look at the most popular SSD articles seen by readers in the past month.

See also:-

Can you trust SSD market data?
where are we now with SSD software?
Recent Strategic Transitions in the SSD market
understanding flash SSD performance characteristics and limitations

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How do you recognize one?

At its simplest - the fast-enough PCIe SSD today - for example - offers similar performance specs to the fastest PCIe SSD from 4 to 5 years ago.

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