
RAMCloud puts everything in DRAM - ukdm
http://www.zdnet.com/blog/storage/ramcloud-puts-everything-in-dram/1546
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fleitz
"Imagine a world where data layout doesn’t matter, where apps are optimized
for sub-millisecond storage, where 100 byte I/Os are faster and just as
efficient as 8KB I/Os. The architectural implications are huge and would take
a decade or more to get our heads around."

Umm.. I've worked with in memory data structures (who hasn't?) and yeah,
layout DOES matter. Especially if your data structure is larger than a cache
line.

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VladRussian
>"Imagine a world where data layout doesn’t matter, where apps are optimized
for sub-millisecond storage, where 100 byte I/Os are faster and just as
efficient as 8KB I/Os.

with latency not being absolute 0, 100bytes I/O will always be less efficient
the 8K I/Os. For example, with 300Mb/s and 0.01ms latency the throughput would
be 10M/s vs 220M/s.

~~~
jasonwatkinspdx
_"100bytes I/O will always be less efficient the 8K I/Os"_

Not if only 200 bytes of that 8K are relevant. It depends on the rpc overhead,
but the small io's may be more efficient. Which is why you see them
researching changes to the networking stack.

 _"300Mb/s and 0.01ms latency the throughput would be 10M/s vs 220M/s."_

When you write numbers on a napkin this is true. When you're talking about
real systems that are both concurrent and scheduled in quantized slices you'll
see much more complex behavior.

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mad44
Here is a summary of the research paper.
[http://muratbuffalo.blogspot.com/2010/12/case-for-
ramclouds-...](http://muratbuffalo.blogspot.com/2010/12/case-for-ramclouds-
scalable-high.html)

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to3m
Is "DRAM" the new name for "RAM"?

Anybody know why the change in terminology? In which circles is this standard?

~~~
antoncohen
> Is "DRAM" the new name for "RAM"? Anybody know why the change in
> terminology? In which circles is this standard?

RAM has always been DRAM. Specifically putting the "D" was probably meant to
differentiate it from other types of Random-Access Memory, like NVRAM.

~~~
effn
The term DRAM is used to differentiate it from SRAM, which is faster but less
dense.

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xtacy
One of the driving goals of putting everything in DRAM was "low latency." They
want latency of retrieving a small sized (100 byte) object to be as low as a
few microseconds, _even across a network_.

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sshirokov
I'm not exactly sure what's being invented here that doesn't exist already.

~~~
jpadkins
can you cite an example of when DRAM is used for persistent storage? I am not
aware of any.

~~~
antoncohen
There are a few products the use primarily DRAM, usually backed by
capacitors/batteries and flash.

ZeusRAM SAS drive: <http://www.stec-inc.com/product/zeusram.php>

RamSan rack-mounted: [http://www.ramsan.com/products/rackmount-ram-
storage/ramsan-...](http://www.ramsan.com/products/rackmount-ram-
storage/ramsan-440)

Kaminario K2 SAN: [http://www.kaminario.com/products/K2-Solid-State-SAN-
Storage...](http://www.kaminario.com/products/K2-Solid-State-SAN-Storage/)

~~~
j_s
Further examples of combo products:

<http://en.wikipedia.org/wiki/IOPS>

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samstave
Am I mistaken, or is this what Violin Memory, FusionIO, and there is a 3rd
company that is doing this already...

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wmf
That's flash, accessed through a block device interface with 10-100 us
latency. RAMCloud is using DRAM with <10 us latency.

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swiecki
It would be cool if they could put everything in SRAM.

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pjscott
At the large sizes they're using, SRAM would be slower than DRAM because of
the longer wire delays that its lower storage density causes.

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herf
redis?

~~~
jasonwatkinspdx
Nope

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rajpaul
This sounds a lot like SAP's in-memory database, HANA:

"SAP HANA is an integrated database and calculation layer that allows the
processing of massive quantities of real-time data in main memory to provide
immediate results from analyses and transactions."

[http://www.forbes.com/sites/sap/2011/10/04/why-sap-hana-
is-a...](http://www.forbes.com/sites/sap/2011/10/04/why-sap-hana-is-a-better-
choice-than-oracle-exalytics/)

