A little-known third and fourth type of SSD is not intended to replace magnetic storage. Instead, these devices are intended to replace RAM.
Mark Grosser, Managing Director of Sydney performance optimisation specialists Protogen, says this class of SSD use SDRAM or DRAM, a form of memory faster than Flash that can be re-written infinite numbers of times. Protogen resells devices from US company SolidData. These rack-mounted machines do much the same job as any other storage device but, unlike disk or other SSDs, cannot store data when switched off.
The role of these devices is therefore to provide super-fast storage for applications that find conventional storage creates an I/O bottleneck.
Why buy a rack-mounted box full of RAM with a fiber channel connector when you could simply pack your server full of the same chips?
Grosser says these devices can bust bottlenecks and improve application performance faster than other storage technologies, and do so more easily than re-architecting either code or servers.
Lower licensing fees are another incentive. “Microsoft enterprise licenses have a cost for the amount of RAM used in the server,” he says. “The bigger license the more RAM you can use.” SDRAM SSDs can therefore effectively give a server more RAM to play with, but without incurring extra software license charges.