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Using RAM as a temporary EXTERNAL storage medium!? RAMdrive

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Hello,

I came across a thread in the forum that almost answered some questions I have regarding using RAM as a storage medium. I'm not a storage pro, but I am tinkering with a temporary storage idea. Before I spend days working on this idea, I need some feedback as to whether the basic concept is feasible.

To greatly oversimplify matters, a RAM module needs two connections in order to function: a data connection and an power connection. When a computer is shutdown, the RAM module loses power and no data is retained.

Let's say that a RAM module was built into some sort of external enclosure. The enclosure has a USB cable to connect to a computer and is powered by an external power source. This would basically be an external hardware RAMdisk. If the power source were never disconnected, could one disconnect the external RAMdisk from one computer and plug it into a second computer without losing data?

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We have a patent pending on a very high-speed solid-state drive that uses DDR3 DRAM.

You're on the right track, but consider these factors:

(1) DRAM is now so very fast, you are hampering your design with a single USB cable

e.g. DDR3-1333 x 8 = ~10,000 MB/second;

(2) a better approach is to resort to a "quad-channel" design using

something like a multi-lane Infiniband cable (4 x SATA channels);

8 channels would be even faster, given SATA channels limited

by the current MAX of 600 MB/second (this is your bottleneck);

(3) those multi-lane cables are standard model SFF-8088 which

connect to the rear panel of PCIe controllers like the Highpoint

RockeRAID 2722; 2 x SFF-8088 cables give you 8 channels:

http://www.newegg.com/Product/Product.aspx?Item=N82E16816115082&Tpk=N82E16816115082

(4) ideally, a SATA-IV enhancement will permit overclocking of such

storage subsystems, e.g. by "syncing" SATA channels with the clock speed and

"jumbo frames" now utilized in PCIe 3.0 chipsets: 8G / ~8b = ~1.0GB/second

per x1 PCIe 3.0 lane; see my Presentation to the Storage Developer Conference

last Fall in Santa Clara, California:

http://supremelaw.org/patents/SDC/SATA-IV.Presentation.pdf

http://supremelaw.org/patents/SDC/Overclocking.Storage.Subsystems.Version.3.pdf

(5) I wouldn't recommend moving such a ramdisk when it is powered ON;

we believe it's better to implement a fast image restore task

e.g. after routine maintenance when the ramdisk must be powered OFF;

(6) yes, as long as a quality battery backup unit supplies input power

to the entire workstation, a very practical solution to external input power

is an auxiliary AC adapter, like those which power Samsung flat panels;

but, in between the battery backup unit and the ramdisk, add a power strip

so you will have a separate ON / OFF switch;

(7) a very exciting future is just now emerging with Non-Volatile DRAM

also known as NV-DIMM; I watched a webinar recently by an expert

at AgigA Tech which covered the state-of-the-art with NV-DIMMs;

Non-Volatile DRAM should eliminate the need for an auxiliary

input power supply like an AC adapter:

https://www.brighttalk.com/webcast/663/95329

Hope this helps.

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p.s. Practically speaking, if your design must use a single USB 3.0 cable,

you would do just as well to go with a USB 3.0 external enclosure for 2.5" drives

and install a good Nand Flash SSD in that enclosure.

Then, assuming the host USB 3.0 port supplies the

required DC power, you won't need any external

auxiliary AC adapter because the required power

is supplied by the host's USB 3.0 port.

At Newegg, search for "USB 3.0 external enclosure"

and find lots of items to choose from.

Here's one that assumes the input power is

provided by the USB 3.0 cable:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817392057&Tpk=N82E16817392057

Be sure also to confirm that your host USB 3.0 port

does provide the required DC output power.

For example, this Highpoint USB 3.0 controller requires a

standard 4-pin Molex connection from the

main ATX Power Supply Unit ("PSU"):

http://www.newegg.com/Product/Product.aspx?Item=N82E16816115105

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