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Zero RPM SSDs killed 20K hard drives
Zsolt Kerekes, editor -
7 years ago I started publishing a new series - the Top SSD Companies which has been seen by over 5 million readers and is now regarded by many key people in the SSD industry (and their investors and biggest customers) as one of the most useful SSD articles which influences their thinking.
the Top SSD Companies
Flash Memory Summit - event logo
That next step - when users make the switch to newer generations of software - means not only do they need less servers - but they don't need as many SSDs as they did in an earlier phase of SSD market adoption either.

Some enterprise vendors have already seen the painful effects - the most notable being Fusion-io.

However it will affect all enterprise SSD vendors at some time or other.
meet Ken - and the enterprise SSD software event horizon

memory channel SSDs

versus PCIe SSDs (revisited)

are these really different markets?

by Zsolt Kerekes, editor - April 17, 2014

18 months ago I published a blog called - Boundaries Analysis in SSD Market Forecasting - which is a technique I've been using for many years to help me judge how new and future SSD technologies can settle into new market uses - and whether they might create new sustainable markets which fit in alongside other competitive solutions.

And that co-existance type of eureka moment - tells you a different kind of story compared to the simpler "this will replace that - because it's cheaper and better" kind of wishful thinking which accompanies many new technology announcements.

When I wrote the original boundaries analysis article - the examples I used in it were already quite old (to me) - and I was just using them to demonstrate how you can analyze the business viability of new SSD market segments many years in the future without having to know in detail how any the specific technology problems will be solved.

(Assuming that they could be solved if it was deemed to be worthwhile - is enough in this context.)

Anyway I returned to that subject in a conversation I had this week about memory channel SSDs versus PCIe SSDs.

In some respects I was returning to some of the core judgements which I published a year ago in my blog Memory Channel Storage SSDs will the new concept fly? - should you book a seat yet?

But that was written before there were any real products based on this technology - so some of my comments were made on guesses.

Since then - we've seen the technology being shipped and adopted by IBM (who worked with MCS's creator Diablo for years and helped shape the architecture and wrote a book about its uses.

And there's an excellent faqs page which tells us almost everything we might wish to know about the technical boundaries of this product.

What about the marketing boundaries?

Here are some question from that angle.
  • if memory channel SSDs cost nothing - would there still be a market for PCIe SSDs?

    and conversely
  • if PCIe SSDs cost nothing - would there still be a market for MCS?
Let's dicuss these hypothetical questions in order.

If memory channel SSDs cost nothing - would there still be a market for PCIe SSDs?

Yes - for 2 reasons.
  • PCIe SSDs fit in more readily to a PCIe fabric connection - from card to card and also between racks. This can be used to provide high availability or scalability or both.

    MCS is currently limited to short line lengths. That's part of what endows it with better latency - but is a restriction too.

    So there would still be some uses for PCIe SSDs if MCS was free (or cheaper).
  • And another reason is that PCIe SSDs can be designed to be hot pluggable - whereas MCS (like DRAM DIMMs) doesn't support hot pluggability.

    So if you have a storage rack which looks like an arrays of 2.5" PCIe SSDs - you can incrmentally add new modules or replace falty modules while the system remains powered.

    Those incremental RAS features - at the drive level - are critical for some markets. So that's another reason why PCIe SSDs would still have a big market even if memory channel SSDs cost the same or less (for equivalent capacity).
And how about my other question.

If PCIe SSDs cost nothing - would there still be a market for MCS?


The main reason is latency.

In currently marketed products - MCS offers typically 5x to 10x lower latency (which can be relied on) than typical PCIe SSDs.

So if ISVs know they can rely on a different class of characteristics - and if they think the market opportunity is big enough to make it worth their while - they can differentiate their product offerings by offering new or differentiated apps functionality in MCS configured servers - which the ISVs can't support in PCIe SSD based servers.

In the same way that people talk about the economic advantages of tiering between different speeds of storage box (in classical hard drive SAN based architectures) so too - when you move inside the apps server box you can get efficiency advantages by being able to tier between different speeds and classes of SSDs.

It was after that kind of analysis that I concluded that memory channel SSDs really are a different type of product which will find their own places in the market - and shouldn't just be regarded as an alternative to some faster types of PCIe SSD.

And that's why they have their own distinct column in my architecture matrix proprosal for SSDserver rank. (Which was the topic of last month's home page blog).

Here's a sanity check.

There's still a lot of software yet to be written by ISVs before you'll see some of the differences between PCIe SSDs and MCS appear in sharper focus. But the business cases are real enough to make it happen.

Are you ready to rethink RAM?

The revolution in use-case-aware intelligent flash could cross over into new enterprise DRAM architecture.

by Zsolt Kerekes, editor - April 2, 2014

In recent years in the flash memory market, we've seen SSD controller designers revisit and challenge the fundamental assumptions surrounding - what's the best way to interact with the raw memory?

And instead of just leaving critical timing parameters "as set" in the factory by "those who know best" (the preset magic numbers which are designed to satisfy worst-case usage within the memory population as a whole) - SSD designers have leveraged the idea that "local knowledge (in a systems context) is better" - to design new adaptive R/W controller schemes which change the raw capabilities of memory arrays - to enable faster speed, or lower power, or better reliability - or a combination of desirable features.

But what about designers in the RAM market?

Apart from 3D, packaging and interplane connection techniques - is there any similar revolutionary thinking going on in the RAM market?


In some random reading I did recently - my attention was drawn to a collection of papers delivered in August 2013 at a conference called MemCon.

I hadn't read these before - partly because I was on vacation at the time - and when that finished - I was too busy catching up with digesting the new ideas which had been channeled through the SSD industry's premier event - the Flash Memory Summit - which took place shortly after MemCon.

If you wondering why I say "FMS is the SSD industry's premier event" - then take a look at how many times it has been mentioned in the same breath as an advanced SSD concept on this site alone.

In 2014 - the relative timings of these 2 events has been adjusted to create a gap which is months rather than days - so that those poor mortals who attend both - get a chance to recuperate.

the new thinking in RAM architecture

For me today - the most interesting of all the RAM related papers on the MemCon site in my reading this week - was one which explored in a modern SSD perspective - the idea of adapting the refresh rates in DRAM to leverage the difference between "worst case" and "good enough" timings. In his presentation - Memory Scaling - a Systems Architecture Perspective (pdf) - Onur Mutlu, Assistant Professor Electrical and Computer Engineering - Carnegie Mellon University called this "Retention-Aware DRAM Refresh".

If you only like to learn one new thing a month - that in itself seems like a good enough place to stop - but it's just one of the warmup steps for the intensive workout which follows.

If you think you may up to that challenge - take a look at Onur Mutlu's accompanying paper - Memory Scaling: A Systems Architecture Perspective (pdf) - which among other things - proposes putting SSD-like thinking into the design DRAM and moving away from the idea of treating "DRAM as a passive slave device."

This paper is rich with ideas such as:-
  • tiering within the DRAM (using 2 level latency-segmented bitlines)
  • moving blocks of data within the RAM - without using the external bus - with a new design and topology of sense amps
And here's a quote from Onur Mutlu's paper which I think resonates with the enterprise SSD experience:-

"Our past work showed that application-unaware design of memory controllers, and in particular memory scheduling algorithms, leads to uncontrolled interference of applications in the memory system. Such uncontrolled interference can lead to denial of service to some applications, low system performance, and an inability to satisfy performance requirements, which makes the system uncontrollable and unpredictable."

So - will we see more flash-controller-like functions inside future DRAMs?

That depends on the system cost-benefits. (And whether such schemes can be implemented in commercially scaled semiconductor layouts - rather than the kind of conceptual lines drawn to connect virtual blocks on a whiteboard.)

Support for embedded controllers is already an integral part of the Hybrid Memory Cube (launched in October 2011) - but Carnegie Mellon's ideas about new memory designs cross the frontier line which artifically separates different chips even within an HMC architecture.

where's the money?

There can sometimes be money to be made from some of these blue sky academic research ideas.

Yesterday for example (April 1, 2014) - Marvell Semiconductor announced that a US court this week determined that the company should pay $1.54 billion to Carnegie Mellon University for alledgedly infringing patents related to hard drive patents. more - Whatever the final outcome of any appeals process - it's keeping some smart lawyers in work.
Hmm... it looks like you're seriously interested in SSDs. So please bookmark this page and come back again soon.
About the publisher - 22 years guiding the enterprise market
BiTMICRO has new VP of Engineering
Editor:- April 16, 2014 - BiTMICRO recently announced that Bharadwaj Pudipeddi has joined the company as VP of Engineering and Lead Architect. Pudipeddi's past design roles in notable SSD companies include 2 years at Violin Memory.
SSD ad - click for more info
3 weeks ago a new record for brevity was established in a new SSD product briefing conversation I had with SanDisk. Because our time ran out - and we never even got as far as page 1 of the briefing document.
what did we talk about instead? (April 15, 2014)
Today - if you're in a big company in a traditional market - and hoping to do something equally big in the SSD market - then $1 billion may not be enough - but $5 billion may be too much.
VCs & SSDs

"SAS SSDs stood out as the stellar performer in the enterprise segment last year - with 69% revenue growth..."
market research news - March 20, 2014

One thing which hasn't changed since the early days of enterprise flash - is the concept of a "naughty" type of flash memory - which sensible, cautious types point at saying - that's never going to be reliable enough.
the evolution of enterprise flash - a 10 year history

LSI blog discusses customer driven technology changes in the hyperscale datacenter
Editor:- March 4, 2014 - "It's no longer enough to follow Intel's ticktock product roadmap" - says Rob Ober, Processor and System Architect LSI - in his new blog about Restructuring the datacenter ecosystem - in which he goes on to say...

"Development cycles for datacenter solutions used to be 3 to 5 years. But these cycles are becoming shorter."

And when talking about rack scale architectures - Rob says "Traditionally new architectures were driven by OEMs, but that's not so true anymore." the article

"The winners in SSD software could be as important for data infrastructure as Microsoft was for PCs, or Oracle was for databases, or Google was for search."
get ready for a world in which all enterprise data touches SSDs

how fast can your SSD run backwards?
SSDs are complex devices and there's a lot of mysterious behavior which isn't fully revealed by benchmarks, datasheets and whitepapers.

Underlying all the important aspects of SSD behavior are asymmetries which arise from the intrinsic technologies and architecture inside the SSD.
SSD symmetries article Which symmetries are most important in an SSD?

That depends on your application. to read the article

"Bottlenecks in the pure SSD datacenter will be much more serious than in the HDD world - because responding slowly will be equivalent to transaction failure."
will SSDs end my bottlenecks? - and cure all my server problems?

"A critical test of whether you really understand the dynamics of a complex market like enterprise SSDs - is whether you can predict what rational buyers might do when offered new product options at the extreme limits of - for example - price."
Boundaries Analysis in SSD Market Forecasting

Can you trust SSD market data?
Heck no!

"Flash wear out still presents a challenge to designers of high IOPS flash SSDs as the intrinsic effects at the cell level get worse with each new (planar) chip generation.

Although 3D nand may be the turning point at which raw intrinsic memory endurance stops worsening (or gets better) - 3D could also introduce new types of failure mechanism and R/W distrurbance sensitivities too."
SSD endurance - the forever war

Raw speed is no longer the same guarantee to market success for SSDs as it once used to be. But since you asked...
the Fastest SSDs

"A new generation of enterprise SSD rackmounts is breaking all the rules which previously constrained price, performance and reliability."
exciting new directions in rackmount SSDs

Usable versus Raw flashcapacity - isn't the full picture.

A lot of flash in SSDs is just plain Invisible.
SSD capacity - the iceberg syndrome

"SSD is going down! - We're going down!"
Surviving SSD sudden power loss

"...the SSD market will be bigger in revenue than the hard drive market ever was."
How will hard drives fare in an SSD world?

"You can't see them - but the gravitational pull from these massive SSD users is changing markets."
The big market impact of SSD dark matter

my flash SSD care management scheme is 100x better
The new fad in selling flash SSDs

"You'd think... someone should know all the answers by now. "
what do enterprise SSD users want?

Here's the real problem for the big companies.

They can lose tens of billions of dollars of future revenue by not participating now in the SSD market.
Hostage to the fortunes of SSD is published by ACSL. © 1992 to 2014 all rights reserved.

Editor's note:- I currently talk to more than 600 makers of SSDs and another 100 or so companies which are closely enmeshed around the SSD ecosphere.

Most of these SSD companies (but by no means all) are profiled here on the mouse site.

I learn about new SSD companies every day, including many in stealth mode. If you're interested in the growing big picture of the SSD market canvass - StorageSearch will help you along the way.

Many SSD company CEOs read our site too - and say they value our thought leading SSD content - even when we say something that's not always comfortable to hear. I hope you'll find it it useful too.

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