Founded in 2003, Diablo is successfully delivering products that enhance
the performance and capability of memory system designs.
Since 2010 - Diablo has been developing an
SSD technology which the company calls Memory Channel Storage which
leverages the disruptive capability of NAND-flash and future
technologies to enable increased levels of application performance supported by
a new class of enterprise server and storage system designs.
The Diablo executive management team, now developing its 3rd family of
memory interface solutions, has decades of experience in system architecture,
chip-set design and software development at companies including Nortel Networks,
Matrox Graphics, Goal Semiconductor, BroadTel Communications, ENQ Semiconductor,
IceFyre Semiconductor, Mosaid
Techologies and Huawei.
- editor mentions on StorageSearch.com,
Memory Channel Storage page
|Diablo replaced Fusion-io as the
#1 most researched SSD company by readers of StorageSearch.com in the
Q3 2014 edition
of the Top SSD
Companies List which was published in December 2014.
who's who in SSD? - Diablo Technologies
editor - May 2014
entered the enterprise
market in 2013 and made its first appearance in the
Top SSD Companies list
in Q3 2013.
technology was described by StorageSearch.com
as being the most significant new form factor for enterprise SSDs in that year.
recently Diablo was ranked #16 in the
Q1 2014 edition of
the Top SSD Companies.
Diablo has created a new reference
architecture for fast low latency
flash memory based
enterprise SSDs - which Diablo calls
StorageSearch.com calls this category of SSDs - which
already includes many brands -
Diablo's MCS SSDs fit into conventional DIMM sockets
which were originally designed to accomodate
positions MCS SSDs as a superior alternative competitor to fast low latency
PCIe SSDs. That
sounds like an elegantly simple marketing message - but the competing
arguments for these technologies are more complicated. For details see
- memory channel SSDs versus PCIe SSDs
are these really different markets? (May 2014).
Unlike all leading
PCIe SSD vendors - Diablo doesn't design and market complete SSDs.
the first MCS SSDs - ULLtraDIMMs - came to market as a design collaboration
with SMART Storage
Systems - which was soon afterwards
first major server maker to publicly adopt Diablo's MCS SSDs was
IBM - which had worked with
Diablo for years to shape the MCS architecture.
IBM's eXFlash DIMMs
(as used in IBM's
January 2014 server annoucements) are simply rebranded SanDisk ULLtraDIMM
Diablo has been working with various
SSD software ISVs to
get support for their architecture as a platform in ways which are different to
It seems reasonable to assume that that sometime in the
future (after what I assume is a period of initial exclusivity with SanDisk)
Diablo will license its interface and software technology to other memory
and systems designers for use in alternative designs of SSD.
future I would be surprised if
Micron didn't also
enter this market with low latency MCS style SSDs too.
In that case
I think the most likely gating factor for that transition would be
volume adoption - in servers - of the Hybrid Memory Cube form factor. That
would enable Micron to combine more of its own memory IP rather than simply
producing a design compatible with DDR-3 or DDR-4.
|I don't think we've reached
stability in reference enterprise SSD designs and use cases.
All the systems in the market today are implementations of transient
architectures which are pragmatically adapting legacy installations and
|what kind of SSD world can
we expect in 2015?|
articles related to
Diablo's place in SSD market
the fastest SSDs
the Top 20 SSD Companies
SSD glue chips and interfaces
SSD silos in the
Channel Storage / ULL SSDs
what's in a number? -
for memory channel SSDs - add 4
enterprise SSD companies have no good reasons to survive
In November 2012
- Diablo Technologies
it has closed a $28 million
funding round which
will help the company
Memory Channel Storage concept to market.
In March 2013 -
announced it has closed an additional $7.5 million of funding, increasing
the total equity investment of its most recent round to $36 million.
- Diablo Technologies
SMART Storage as
its exclusive flash partner to pioneer a new type of (faster than
PCIe SSD) memory
In August 2013 -
it had begun sampling the first memory channel SSDs compatible with the
interface and reference architecture created by Diablo Technologies.
January 2014 -
its first servers - using eXFlash DIMMs - which is IBM's name for the flash
SSDs designed by SanDisk
which are based on the
Storage architecture invented by
Diablo. Read more in the
article - It's IBM
Jim - but not as we know it
Also in January 2014 -
it had filed motions to add 2 additional patents to the lawsuits against the
previously announced ULLtraDIMM memory module from
Diablo Technologies and
Smart Storage Systems.
announced details of a new 2nd generation
SSD - low latency flash SSD accelerators in DDR-4 sockets - which will
sample in the first half of 2015.
changed in SSD year 2014?|
enterprise SSD users want?
11 key symmetries in
big market impact of SSD dark matter
thrive guide to enterprise SSDs
Auto-tuning SSD Accelerated
Pools of storage
don't all PCIe SSDs
look pretty much the same?
Efficiency as internecine
SSD competitive advantage
discusses details of Memory Channel Storage|
|Editor:- July 30, 2013 - Diablo Technologies
today did the
public launch of
its its new technology -
Memory Channel Storage
- which repurposes the interface and form factor of server DRAM into a new
architecture for ultrafast flash SSDs which the company positions as a
competitive alternative to very fast
PCIe SSDs. |
comments:- I spoke recently to Diablo's new VP of Marketing - Kevin Wagner about the
company's new MCS.
I had already gleaned a heads up on the boundary
capabilities and market potential of the new technology in
interview with Diablo's flash partner SMART. So it was natural to ask how
Diablo viewed the impending acquisition of
surprisingly Kevin indicated that whereas Diablo already thought it had made the
best choice before - the upside potential of having SanDisk as a partner for
this memory technology made it 10x better.
Here's what I
- Diablo's TeraDIMMs are designed to fit standard sockets designed for DDR-3.
They are electrically, form factor and power compatible. But instead of RAM - a
typical TeraDIMM using today's technology might have 400GB of flash.
- Diablo's controller architecture means that the host CPU can read and
write from memory in the same transparent way as it would talk to RAM.
- TeraDIMMs can be installed in every set of slots where you'd normally
insert RAM. The only limiting factor in the current architecture is that at
least one pair of slots has to be RAM. All the rest can be flash.
- Diablo claims that MCS has better write latency than most PCIe SSDs.
Specifically MCS has a write latency of 3 to 5 microseconds. This is
really a write to the controller.
TeraDIMMs have a
architecture - which means that apart from a small amount of register
memory in the MCS controller itself - no
RAM is used in the SSD.
The MCS design includes
hold up capacitors which guarantee that all data which has been written to
the TeraDIMM gets completely saved to flash.
- From the applications point of view MCS looks like a massive amount of
persistent RAM - but with terabytes rather than tens of gigabytes of memory
space and with a cost structure closer to the
market price of flash
the product is not yet available - Kevin Wagner told me that Diablo has been
getting a lot of interest from server companies. Diablo has been validating
software with their ASIC based implementation for several months following good
earlier characterizations of the design with FPGA. From the software point of
view Diablo's aim was to prioritize a usable design which would work for the
market as soon as possible. Obviously many possibilities for leveraging the
basic technology spring to mind. I asked for example about preferred models of
- Is it bootable? No. Not yet that wasn't regarded as a priority.
Kevin said that so many companies are interested in
what they're doing that they don't have enough resources to talk to them all
right now. It won't be long before the company publishes more details of its
reference architecture - and conversations have already begun with ISVs and
other companies which could be the seeds of a new ecosystem.
current design has been designed to work in virtualized and non-virtualized
environments and the company has got already got a good idea of how headline
big data apps would perform in benchmarks using their technology.
raised the question of inter-operability with
PCIe SSDs (in the same
MCS resident servers) and it looks like the guesses I had made about
segmentation and collaboration and competition with other SSD types which I've
about in my earlier article about memory channel SSDs - are still valid. So
I won't repeat those points here.
We still have to wait for firm
product pricing and configuration details. But if you had any doubts about where
the money will be inside servers - MCS provides another new way of packing
even more flash SSD capacity in.
|more money for Diablo|
|Editor:- March 19, 2013 - It's
not unusual in the current
SSD market for
some companies to have oversubscribed
rounds - and that was the case recently with Diablo Technologies
it has closed an additional $7.5 million of funding, increasing the total
equity investment of its most recent round to $36 million.
previously announced investors.|
Editor's comments:- Diablo
describes its product as being these categories:- "soon-to-be-announced"
If you're already interested in
InfiniBand or SSDs
in RAM module form factors
(but which unlike the flash DIMMs from memory makers - might actually emerge
from stealth mode attached with a software model) then what Diablo does do
with its Memory Channel Storage may impact some of your future long range
Like you - I'm guessing of course. Diablo hasn't ordered any SSD
ads yet - although that $7.5 million would come in handy.
|Diablo names SMART Storage
as exclusive flash partner to pioneer memory channel SSDs|
|Editor:- April 25, 2013 - You may remember
reading here before about a company called Diablo Technologies -
which while in stealth mode - hinted it was working on a new technology which
would enable SSDs to run on server motherboards with latency and throughput even
better than PCIe SSDs....
Diablo has been creating the interface side of things - but I learned
recently that implementing the flash side of this - in a manner which is both
effective and affordable - requires a world leading mastery of enterprise flash
IP - which Diablo wisely recognized it doesn't have.
has publicly announced an exclusive partnership agreement with SMART Storage Systems
which will leverage its flash IP and controller assets to co-design a new family
of ultra-low latency SSDs and system accelerators which connect via Diablo's
memory channel storage architecture and which will be sold exclusively by
SMART but jointly supported by both companies.
comments:- there are a lot of implications for the future direction of SSD
server acceleration if this collaboration succeeds in delivering competitively
attractive new types of SSDs. But there are also very difficult technical
problems and ecosystems development problems to solve too in order to make it
I discussed these topics in a conversation earlier this week
with John Scaramuzzo,
President and Esther Spanjer,
Director SSD Marketing at SMART.
Among the many questions inspired
by that conversation:-
- how is the new technology different to what has been done before? -
particularly with PCIe SSDs and with DIMM class flash?
- if successful - what impact would memory channel SSDs have on the PCIe SSD
market? - and application server architecture?
- how will the new types of SSDs stretch the demands of flash endurance and
- how will competitors respond to this new technology? And how much of what
they say should you take take on board or disregard?
- who are going to be the among the first wave of customers to adopt these
I've written about these
matters and more in a new home page blog on StorageSearch.com -
Storage SSDs - will the new ultra low latency SSD concept fly? - should you book
a seat yet?
- when will the first products be ready?
up advisory team for new SSD interface|
|"As we prepare to launch our line of Memory
Channel Storage products that enable next-generation enterprise server and
storage system designs, we have set our sights on unprecedented levels of
performance for current and future applications To that end, we have
a group of top industry innovators to help refine the development of our
revolutionary NAND-flash system solutions... |
Maher Amer, CTO
January 29, 2013
|New to me
in SSD - Diablo Technologies|
|Editor:- November 8, 2012 - every week I learn
about new SSD companies and today one of them was Diablo Technologies -
which is working a new high speed direct attach like memory nand flash (and
maybe other nvm) SSD controller / product concept which it calls
it has closed a $28 million funding round which will help the company bring
their concept to market.
With this equity funding we are accelerating
the completion of a memory channel-based solid-state storage platform that will
deliver breakthroughs in system performance and flash storage density for
analytic data processing, web-page serving, cloud computing and other
server-based enterprise computing applications said Diablo's CEO and founder -
background is in chips (ASIC+FPGA), telecomms and DRAM memory. I haven't
spoken to anyone in the company yet.
But if I had to make a wild
guess it would be that Diablo's product may be something like
other PCIe SSD in
architecture - but packaged more like
compatible flash SSDs in form factor and connectivity.
note:- "What Diablo is doing is effectively creating a new layer in
the memory/storage hierarchy" said one of Diablo's investors Alex Benik in his
today explaining why he likes the company. "Diablos MCS-based products
will be dramatically higher capacity than DRAM, persistent, and deliver more
IOPS at lower latencies than any other SSD technology."
|Diablo's roadmap back on
track following jury verdict|
|Editor:- March 25, 2015 - Diablo today
it has won a "decisive victory" in its critical court battle with
The jury unanimously concluded that there was no breach of contract and
that there was no misuse of trade secrets. Further, the jury confirmed Diablo's
sole ownership and inventorship of the "917 patent."
are extremely pleased with the jury's verdict today," said Riccardo
Badalone, CEO and Co-Founder of Diablo Technologies. "We look
forward to getting back to serving our customers and delivering on our exciting
Memory Channel Storage roadmap."
Editor's comments:- Diablo replaced
Fusion-io as the #1
most searched SSD company by the readers StorageSearch.com in
Q4 2014 - because
you all know a disruptive SSD technology platform when you see it.
long running legal tangles got to the point where Diablo was prevented by an
injunction from making more products - pending a trial outcome. This verdict
means the enterprise application acceleration industry can resume its onwards
progress by being able to count on the availability of a significantly
flash latency asset
and software platform for deployments inside the server box.
Diablo appeals shipment injunction - says court was misled|
|Editor:- January 14, 2015 - Diablo Technologies
that it has appealed the court ruling (reported earlier this week -
and initiated by Netlist)
which had granted a preliminary injunction to halt Diablo's shipments of Memory
Channel Storage based chipsets. |
Diablo's appeal explains that the
ruling is based on an erroneous interpretation of the contract and a failure to
recognize the technology differences among the products involved.
importantly, however, the court did not find that Diablo MCS uses
Netlist trade secrets.
Diablo says - to support the judgment, the
order effectively rewrites the language in the contract signed by the parties in
2008: the additional words included in the order changed the terms of the
contract significantly and imposed a new obligation that was not agreed between
the parties. In other words, there was no violation by Diablo of the original
contract. The court was misled about important technology distinctions:
court relied on Netlist's representation that their HyperCloud and Diablo MCS "are
used to perform the same function" which is not the case because the
HyperCloud is DRAM (memory) and Diablo MCS is a block storage device (disk).
The court also relied on Netlist's representation that the products
are competitive because they both "attach to the same memory channel."
Diablo also says "Netlist equates the 2 devices simply because
they use the same location and i/o channel; extending that logic would equate
all devices that reside in PCIe slots, which would be a similarly erroneous
"It is important that the facts of the case are well understood;
it should also be stressed that the court did not determine that Diablo uses
Netlist trade secrets," stated Riccardo
Badalone, CEO and co-founder of Diablo Technologies. "We offer an
innovative storage device that gives customers great performance advantages, but
with this injunction, the court is putting our company and our customers at
risk. With this appeal, we expect to reverse this decision and get back to
Editor's comments:- are Netlist's products functionally
different to those using Diablo's architecture?
Yes! The differences
are so great that the 2 products are listed in different directories here on
Channel Storage SSDs - which encompasses low latency, fast flash SSDs which
plug into DIMM sockets and transfer data via interfaces which were originally
designed for DRAM.
The fact that standards organizations and some vendors have
historically used the term "flash DIMM" in the context of both types
of products - has contributed to industry confusion.
- hybrid DIMMs, NV
DIMMs, flash backed DRAM DIMMs - which includes DRAM modules which
automatically save their contents when electrical power drops to an integrated
non volatile memory from which the data is reloaded after normal power is
But the term -
flash DIMM - is a description of the physical form factor - and tells you
nothing about the operation and functionality of the device from a data
architecture point of view.
The differences are vast and immediately
obvious to anyone who's technical. But I was wondering how would I explain the
gulf of difference to someone who doesn't know anything about computer design.
analogy goes like this... Suppose someone offered you the choice of 2 types of
backpack when you started a balloon ride.
One is a parachute, the
other is a jetpack.
They both perform different functions - although -
until you activate their functions they both might look the same.
I know you need a higher skillset to operate the jetpack.
also need a much more developed
SSD software support
ecosystem to deploy memory channel SSDs too.
|Diablo countersues Netlist
|Editor:- September 25, 2014 - Diablo announced today
that is has filed a lawsuit against Netlist for unfair
business practices that violate Diablos IP rights.|
This appears to be
a countermeasure to 2 earlier lawsuits initiated by Netlist against Diablo -
which were widely reported by the SSD related press in
- Diablo reiterates that its
Channel Storage (DDR3/4 form factor
and interface compatible flash SSD) is a new and innovative architecture
that neither infringes upon, nor misappropriates any Netlist IP rights. And
Diablo argues that its MCS-based products and the
HyperCloud DIMM (high
density DRAM) - which were the cited products in Netlist's earlier legal
moves - are designed to serve different purposes and are not
Diablo says the contract between the 2 companies (which have been
mentioned in the press) clearly assigns legal ownership of the implementation
IP in the HyperCloud chipset to Diablo. As a result, Diablo is seeking damages
for breach of contract for Netlists attempt to usurp the companys IP rights.
We have been very patient throughout this entire process and it is
now time for us to share our side of the story" said Riccardo
Badalone, CEO and Co-founder of Diablo Technologies. "We will
demonstrate definitively that products based on the Memory Channel Storage
architecture do not use any Netlist IP.
| Diablo unveils DDR-4
flash DIMM SSDs|
|Editor:- August 7, 2014 - Diablo yesterday
announced details of a new 2nd generation
SSD - low latency flash SSD accelerators in DDR-4 sockets - which will
sample to oems in the first half of 2015.|
Along with the new hardware
technology there will be an improved software platform - with features like
NanoCommit - which Diable says will enable hundreds of millions of
transactions per second, with nanosecond latency.
Storage DDR4 solutions represent the next evolution of Server Acceleration
technology," said Riccardo
Badalone, CEO and Co-founder of Diablo Technologies. "In addition
to supporting a faster memory interface, the Carbon2 platform delivers
unprecedented levels of hardware acceleration for new software innovations like
NanoCommit. Converged Memory, where the best of Flash and DRAM are combined,
will rely on this type of technology to give applications the ability to
transparently persist updates to main memory."
comments:- After FMS - Diablo sent me
more info (pdf)
about their FMS
presentation (pdf) from which I have extracted these key features.
- Diablo's converged memory architecture (flash tiered with DRAM) is planned
to support 700 million random cachelines / sec.
- Latency of each cacheline is about 48 nanoseconds.
- Diablo's NanoCommit supports byte addressable small writes to flash with
high transaction rates and the ability to mirror the DRAM contents to
- The combination of technologies would enable something like a 1U server
with 25TB of converged memory.
|Diablo secures patent
related to MCS technologies|
|Editor:- July 31, 2014 - Diablo today
that the US Patent and Trademark Office (USPTO) awarded U.S. patent No.
8,713,379, entitled a System and method of interfacing co-processors and
input/output devices via a main memory system, to the company. The 379 patent
- A method for connecting non-volatile memory directly to the memory
controllers of a processor.
- A learning machine to handle data interleaving/de-interleaving and data
scrambling/de-scrambling algorithms for DDR3/4-based memory
- A method to remap the non-linear DIMM address space back to linear address
space used by the driver
|what impact will SanDisk's
acquisition of Fusion-io have on the memory channel SSD market?|
|Editor:- June 17, 2014 - The general implications
announcement yesterday - that it has agreed to acquire Fusion-io - are
discussed in an article on the main
SSD news page.|
But there are special questions which relate to the
emerging memory channel SSD market too. Such as:-
- what if SanDisk acquires Diablo?
- could SanDisk get useful results and new products by combining elements of
current UlltraDIMMs with Fusion-io software?
See my blog -
memory channel SSDs
versus PCIe SSDs (another slight return)
- could SanDisk reduce the power consumption of future UlltraDIMMs by
designing a microcontrollerless Fusion-io style of SSD in a Diablo style DIMM
whitepaper from Diablo looks at|
"drawbacks of traditional PCIe SSDs"
|Editor:- April 22, 2014 - Diablo Technologies
today published a white paper
Storage Performance: it's all about the Architecture (and not just the
|This paper presents Diablo's perspective - as
the creator of
Storage and looks at the measured performance weaknesses of some specific
(but unnamed) PCIe SSDs
with respect to their measured performance
under various loads and then attempts to generalize those weaknesses as part
of an argument that MCS is a better solution than PCIe SSDs - because MCS is
more scalabe and doesn't suffer from the same kind of architectural
comments:- Does the performance data in this paper demonstrate that one
model of fast SSD can be faster or operate more consistently than another?
Yes. (If you choose both the benchmark and the configuration - and
number of SSD controllers in the mix.)
But it doesn't prove the
general proposition that MCS SSDs are better than PCIe SSDs.
years - competing PCIe SSD makers used to publicize
comparisons between their products and those of PCIe SSD competitors. (And
before its acquisition last year -
Virident became a
grand master at publishing this kind of benchmark.)
So while I am
convinced of the benefits of Diablo's MCS architecture - and what it can do
differently and better compared to PCIe SSDs - I think this particular paper
isn't the best evidence for their case.
|Diablo comments on legal
barbs cast by Netlist|
|Editor:- February 14, 2014 -
Diablo's CEO and
Badalone was reported to have said in an
blog by Willem ter Harmsel today - re the lawsuit launched againts
them by Netlist...|
(Netlist) basically have yet to prove that:- they understand the product, and
also that they have found anything Diablo is actually infringing on. We are
just going to let this run through the (legal) process and we are confident
about the outcome." ...read
|Netlist says ULLtraDIMM
SSDs infringe patents|
|Editor:- January 29, 2014 - Netlist today
it had filed motions to add two additional patents to the lawsuits against the
ULLtraDIMM memory module from
The 2 newly added patents (U.S. Patent Nos. 7,881,150
and 8,081,536) are generally related to load reduction, a critical feature in
low latency memory modules. Netlist has now asserted a total of 7 patents
against the ULLtraDIMM, in addition to trade secret theft, trademark
infringement and other claims.
"We have spent years developing
our industry-leading technology, and are encouraged by the progress we've made
defending our intellectual property in these lawsuits," said Netlist
President and CEO, C.K. Hong. "We
will continue to vigorously defend our IP, uncovering any and all theft of our
technology and infringement of our patents, and will not allow others to profit
from this unlawful activity."
in its 8-K last December, Netlist says it received a whistleblower letter
describing in detail how Diablo "stole Netlist's detailed architecture and
design" of its flagship product, HyperCloud, to create the ULLtraDIMM.
comments:- SanDisk's ULLtraDIMM is a
new class of
product in which cheap high capacity
MLC flash emulates many
DRAMs in a module which
contains little or no DRAM itself but which nevertheless plugs into a DDR3
In contrast - Netlist's "similar sounding but very
different" product families include real DRAMs which accomplish power
fail data protection aka non volatility - by means of fast backup and
restore to onboard flash - all in the same DDR3 module.
doesn't appear to be saying that it could design a product like the ULLtraDIMM -
because it doesn't to my knowledge have the
controller IP to do anything remotely similar.
Instead - what
Netlist appears to be saying is that techniques in DDR3 design - which enable
lots of circuitry to be placed behind a RAM interface - without placing too
much load on it and slowing it down - which Netlist has itself patented - are
suspected to have been used within the design of the ULLtraDIMM.
|IBM launches first memory
channel SSD servers|
|Editor:- January 16, 2014 - IBM today disclosed
preliminary test results comparing the latency of
SSDs to PCIe SSDs
- in the
press release of its new X6 architecture for X86 servers. |
- "Our evaluators are seeing 5-10 microseconds write latency for eXFlash
DIMMs in preliminary testing vs. 15-19 microseconds latency for PCIe-based flash
storage from Fusion-io,
Virident, and 65
microseconds latency for Intel
S3500 and S3700 SSDs."
|memory channel SSD vs PCIe
SSD write latency - initial 3rd party benchmarks|
|Editor:- November 7, 2013 - Although it's
possible to make estimates of how a new type of
will perform compared to what already exists - the interplay of applications
software, systems software and a new
controller design -
means that initial assumptions can easily be out by a factor of x2.
And even if you have accurately guessed what the weak points and the
strong points are in the product's
symmetries - it's only when you start to see
that you can have more confidence in your
models of what's
So if you've been wondering how Diablo's
storage compares with PCIe
here to a new whitepaper (pdf) which includes some useful data. The
application isn't important but it's the first public glimpse which goes
usefully beyond the graphs shown in the product launch documents.
highlight for me is - a mean write latency of about 30S for MCS compared to
about 100S for PCIe SSD- at a particular R/W ratio which may of course look
nothing like your own setups.
|When you stop and think about it - we might see
just as large a difference between
models of PCIe SSDs - and as we don't know the identity of the mysterious
"PCIe SSD" in this paper - and as we've only got a very limited view
of the comparison - you might say this whole paper is null data.|
other hand - being able to show that in one situation an MCS SSD can be 3x
faster than a hypothetical PCIe SSD - suggests that the new MCS SSDs aren't
My best guess back in
was that there would be no material performance difference between an MCS SSD
and a best of breed PCIe SSD - when working with best of breed VM optimized
I think the differences between memory channel and PCIe
for server SSDs shouldn't be seen simply as performance differences (which may
indeed not be that significant) but as different integration approaches
which offer a different set of branching out directions depending on the
software environment and the
high availability framework.
The 2 types can even work together in the same server in different roles.