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John W. Verity

Non-Volatile DRAM Is Poised to Give Apps a Big Boost

John W. Verity
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MRFS
MRFS
12/5/2013 6:53:45 PM
User Rank
Kilo
Re: Nn-volatile memory
>  Writes can take longer

That only makes sense:  as long as a string of binary digits remains intact in the storage medium where it was initially stored, and does so until an exact copy can be confirmed in some other non-volatile medium, that "longer write time" is a small price to pay for the all-important integrity which you are so rightly stressing. 

This price becomes much more important when real-time "transactions" consist of multiple discrete binary strings that must all be stored as a group or consistent "set". 

A perfect example of the latter is an HTML file written by MS WORD, which stores any number of graphic images in a Windows sub-folder e.g. filename_files .

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JimOReilly
JimOReilly
12/5/2013 6:39:20 PM
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Blogger
Re: Nn-volatile memory
If your system is Linux, look at using asymmetric mirrors, with NVRAM and an SSD/HDD. Writes can take longer, but reads come from the preferred RAMDisk.

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MRFS
MRFS
12/5/2013 6:28:50 PM
User Rank
Kilo
Re: Nn-volatile memory
Both good comments, Jim.  My work concentrates on increasing productivity on a custom workstation (home-grown) that accesses the Internet quite often. 

Several years back, we discovered RamDisk Plus by superspeed.com, and after hands-on experience I ended up writing a very favorable review of that software, which the vendor liked very much. 

RamDisk Plus has a feature which saves a ramdisk's contents at shutdown and restores it at startup.

FWIW, with the combination of modern DDR2 and DDR3 SDRAM, e.g. Corsair, Kingston, Crucial, G.Skill, plus a quality UPS, my production workstations rarely halt or freeze any longer:  it happens, but not very often -- maybe once every 4 months. 

A 12GB ramdisk stores a 10GB HTML database -and- the browser caches for MSIE, Firefox, Opera and Chrome browsers.  Those browsers use default settings to revert to the Internet if/when the ramdisk does not have a recent copy of the requested file(s) in that ramdisk "cache". 

It wouldn't be too difficult to program applications to fetch a file from non-volatile storage, like a RAID array of SSDs, when a "cache miss" occurs. SuperSpeed already developed software which exploits a ramdisk as a "SuperCache" (their trademark name for that software). 

Perhaps we should enlarge our definition of "NV" to include also Cloud-based servers as one among several ways of handling a cache "miss". But, that shifts the "NV" requirement to the server, and we're right back where we started :)

Similarly, Internet browsers and other application software could be programmed to search multiple different locations when a browser cache "miss" occurs, and not merely request the Internet copy.  Browsing "where" is the operative term here.

In any event, a reliable NV-DIMM is certainly a superior way to host ramdisks, as compared to traditionally volatile DIMMs that are now running in billions of PCs and workstations, particularly when an entirely new file must be stored the very first time.

(Forgive me if I've been too wordy:  I just discovered you folks.)

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JimOReilly
JimOReilly
12/5/2013 5:32:42 PM
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Blogger
Re: Nn-volatile memory
One challenge with in-memory operation is the need for mirrored copies of the data for integrity.

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JimOReilly
JimOReilly
12/5/2013 5:31:09 PM
User Rank
Blogger
Re: Non-volatile memory
Adrian, In-memory databases would really perform if the need to offload data to disk were removed. With BIOS changes, NVRAM will also impact non-stop systems from medical robot surgery to weapons systems and self-driving cars. Rebooting those with traditional drives takes far too long.

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MRFS
MRFS
12/5/2013 4:18:57 PM
User Rank
Kilo
Re: PCs, too?
You can closely approximate a very similar implementation by starting with a tower chassis that has room for 2 x PSUs:  we did that a while back, using an old AT-style PSU as the second of 2 PSUs in that chassis, because those AT-style PSUs have their own ON/OFF switch that is not affected by a SHUTDOWN command.  One of those PSUs can be powered by a dedicated UPS and supply power to an SSD subsystem that stays ON even after a full SHUTDOWN.  What's emerging lately are complaints about retail SSDs that aren't too happy when sudden power loss occurs.  A second variation is to power that SSD subsystem with an external AC adapter like those which come with flat panel monitors e.g. some of Samsung's monitors come with such an AC adapter.  The cabling can pass thru an empty PCI slot in the chassis, or an empty water cooling port.  Admittedly, the DDR DIMM slots in both instances are NOT "NV", but the PC and workstation world may not really need such elegant NV-DIMMs with supercaps etc.  For myself, I cannot imagine a powerful workstation that is NOT powered by a quality UPS e.g. Office Depot now sells CyberPower units with a pure sine wave output.

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MRFS
MRFS
12/5/2013 4:07:37 PM
User Rank
Kilo
Re: Nn-volatile memory
Yes, Jim:  a 1TB DRAM subsystem offers the opportunity to install an OS directly into RAM, rather than installing it initially to rotating HDDs or SSDs.  As such, the OS will also benefit directly from the much higher bandwidth, not merely database-intensive applications.  Think LAUNCH delays that always occur when program files must be read from non-volatile storage, and swap file performance.  FYI:  I submitted a Provisional Patent Application several years back, proposing BIOS changes to make such an idea a reality.  UEFI subsystems are purr-fect for implementing this type of change.

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MRFS
MRFS
12/5/2013 3:59:31 PM
User Rank
Kilo
Re: Nn-volatile memory
The SNIA.org webinar today (12/5/2013) by Jeff Chang was excellent and very interesting e.g. Supermicro have integrated NV-DIMM logic into some of their server motherboards.  And, yes, I agree that such motherboards could be modified with a dedicated power input circuit to supply UPS output directly to DIMM slots.  One implementation option is to provide a motherboard jumper to switch the DC power source between 2 options and/or a BIOS setting to accomplish the same thing.  And redundant PSUs could be modified to dedicate one side of such PSUs to supplying input DC power to those DIMM slots.  I'm remembering way back to 1980 when I toured the mainframes at a large insurance company north of San Francisco:  they had installed a huge 2-story diesel generator which switched ON automatically.  Uninterrupted power has become a very important utility worldwide, e.g. think hospital surgery, emergency rooms and ICUs, as just 3 common examples.

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AdrianProctor
AdrianProctor
11/19/2012 12:10:14 PM
User Rank
Tera
Re: Non-volatile memory
There will certainly be some OEMs that will start with Sandy Bridge - the value prop is clear & they are very excited to integrated ASAP.  But yes, Ivy Bridge is when the volume really gets going... feel free to contact me direct for more specific info... 

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Geoff
Geoff
11/19/2012 11:59:30 AM
User Rank
Kilo
Re: Non-volatile memory
Thank you for your post. So really not until Ivy Bridge EP? Thanks, there has been significant speculation on how this DRAM-Flash (Hybrid Memory) could become a significant technology.

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