NVDIMM

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A Non-Volatile Dual In-line Memory Module (NVDIMM) is a random-access memory for computers. "Non-volatile" means that the memory retains its contents even when electrical power is removed either from an unexpected power loss, system crash, or normal shutdown. "Dual in-line" identifies the product as using the DIMM package. NVDIMMs improve application performance,[1] data security, and system crash recovery time. They enhance SSD endurance and reliability.[2][3]

"Non-volatile" products may use volatile memory during normal operation and dump the contents into non-volatile memory if the power fails, using an on-board backup power source. Volatile memory is faster than non-volatile; it is byte-addressable; and it can be written to arbitrarily, without concerns about wear and device lifespan. However, including a second memory to achieve non-volatility (and the on-board backup power source) increases the product cost compared to volatile memory.

Types[edit]

There are three types of NVDIMM implementations by JEDEC Standards org:[4][non-primary source needed]

  • NVDIMM-F: DIMM with flash storage. System users will need to pair the storage DIMM alongside a traditional DRAM DIMM. NVDIMM-F has been available since 2014.
  • NVDIMM-N DIMM with flash storage and traditional DRAM on the same module. It presents a volatile memory to the computer like any other DIMM. A typical method of achieving non-volatility is to copy information to the non-volatile memory, invisibly to the computer, even in the case that the computer's power fails.
  • NVDIMM-P specifications will be released by JEDEC around 2018[5] It will allow storage inside computer main memory, using ReRAM technology, and a DDR5 interface. A NVDIMM-P has persistent DRAM, and can access external block-oriented (flash memory) drive for memory cache.

Non-Standard NVDIMM implementations:

  • NVDIMM-X: DDR4 DIMM with NAND Flash storage and volatile DRAM on the same module, developed by Xitore.

As of November 2012, most NVDIMMs used NAND flash as the non-volatile memory.[6] Emerging memory technologies aim to achieve NVDIMM without a cache or two separate memories. Intel and Micron have announced use of the 3D XPoint non-volatile memory technology in NVDIMMs,[7] and Sony and Viking Technology have announced an NVDIMM-N product based on the ReRAM technology.[8]

Backup power[edit]

NVDIMMs evolved from the BBU (battery backed up) DIMM, which used a backup battery to sustain power to a volatile memory for up to 72 hours. However, batteries are disfavored in computer components because they have a limited lifespan, they may be regarded as hazardous waste, and they contain heavy metals which violate RoHS compliance.

When the module includes non-volatile memory, on-board backup power is only required for a short time after the computer's power fails. Therefore, modern NVDIMMs use supercapacitors to store energy.

Interface[edit]

A few server vendors, such as Supermicro, still make products using the DDR3 interface to the computer, but standardization work in 2014 and 2015, such as at JEDEC[9] and ACPI,[10] was based on the DDR4 interface.

Uses[edit]

The BBU DIMM was originally designed for use as the cache of RAID HBAs (host bus adapters) or systems, to enable data in the cache to survive a power failure. NVDIMMs have moved beyond RAID applications into fast storage appliances or in-memory processing for the data center and cloud computing.[11]

See also[edit]

References[edit]

  1. ^ "Whole-system Persistence with Non-volatile Memories". microsoft.com. Retrieved 2014-05-08. 
  2. ^ "The Bleak Future of NAND Flash Memory". microsoft.com. Retrieved 2014-05-08. 
  3. ^ "SSDs Risk Massive Data Loss". Storagenewsletter.com. 2013-03-11. Retrieved 2013-09-06. 
  4. ^ "Welcome to the era of NVDIMM Cards". plexistor.com. Retrieved 2015-08-23. 
  5. ^ [1]
  6. ^ http://www.storage-switzerland.com/Blog/Entries/2012/10/2_Does_DRAM_Storage_Still_Make_Sense.html
  7. ^ "Intels crazy fast 3D XPoint Optane memory heads for DDR slots but with a cache". PCWorld. Retrieved 2015-08-21. 
  8. ^ Gil Russell (11 August 2015). "Viking technology and Sony in ReRAM memory mashup". TechEye.net. Retrieved 2015-08-11. 
  9. ^ "JEDEC announces support NVDIMM hybrid memory modules". JEDEC. Retrieved 2015-05-26. 
  10. ^ Michael Larabel. "ACPI 6 Non-Volatile Memory Device Support NFIT libND For Linux". Phoronix. Retrieved 2015-05-21. 
  11. ^ "John W. Verity - Non-Volatile DRAM Is Poised to Give Apps a Big Boost". Datacenter Acceleration. Retrieved 2013-09-06. 

External links[edit]