Christopher George wrote:
What is a "NVRAM" based SSD?
It is simply an SSD (Solid State Drive) which does not use Flash,
but does use power protected (non-volatile) DRAM, as the primary
storage media.
http://en.wikipedia.org/wiki/Solid-state_drive
I consider the DDRdrive X1 to be a NVRAM based SSD even
though we delineate the storage media used depending on host
power condition. The X1 exclusively uses DRAM for all IO
processing (host is on) and then Flash for permanent non-volatility
(host is off).
NVRAM = non-volatile random access memory. It is a general category.
EEPROM = electrically-erasable programmable read-only memory. It is a
specific type of NVRAM.
Flash memory = memory used in flash devices, commonly NOR or NAND
based. It is a specific type of EEPROM, which in turn is a specific
type of NVRAM.
http://en.wikipedia.org/wiki/Non-volatile_random_access_memory
http://en.wikipedia.org/wiki/EEPROM
http://en.wikipedia.org/wiki/Flash_memory
He means a DRAM based SSD with NVRAM (flash) backup vs. SSDs that use
NVRAM (flash) directly. This class of SSD may use DDR DIMMs or may be
integrated. Almost all of these devices that retain their data upon
power loss are technically NVRAM based. (Exception could be a hard
drive based device that uses a DRAM cache equal to its hard drive
storage capacity.) It is effectively what you would get if you had a
regular flash based SSD with an internal RAM cache equal in size to the
nonvolatile storage plus enough energy storage to write out the whole
cache upon power loss.
I doubt there would be any additional performance beyond what you could
see from a RAMDISK carved from main memory (actually there would
probably be theoretical lower performance because of lower bus
bandwidths). It does effectively solve the problems posed by
motherboard physical RAM limits and of an unexpected power loss due to
failed power supplies or failed UPSes.
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