Flash storage devices, or solid state drives (SDDs), use solid state devices to store data. There is no spinning disk or moving disk controller, so there is less latency (wait time also called “seek time”). The SAN card you plug into your camera or cell phone is an example of flash storage. SSD is not the same as the memory in your computer (dynamic random access memory or DRAM) as data stored there does not persist (remain) when you power off the device.
Flash storage devices typically cost more than hard disk drives (HDD), so they are traditionally used in applications where performance is paramount. Some storage systems are a hybrid of SSD and HDD where certain operations, like caching, can write to or read from flash storage first and then write changes back to the hard disk later. Such storage is called “flash-optimized systems.” It uses flash to give a boost to performance.
Some storage systems are all-flash. All-flash-based cards typically plug right into the PCI slot of the server. OCZ Enterprise and Oracle are examples of companies that make these devices. Dell, furiously trying to run away from the low-margin PC business, has entered the flash storage market as well. These are not the same as enterprise storage arrays.
Building SSD arrays, analogous to SAN but using an array of SSDs instead of hard drives, is the goal of Texas Memory Systems, who was recently bought by IBM. They call their products the “IBM FlashSystem.”
IBM has several models offering up to 20 TB of storage. The larger devices use eMLC (enterprise multi-level cell) as opposed to SLC (single-level cell) storage cells. Multi-level cell (MLC) means that one cell of flash memory can hold more bits of data than SLC. Flash storage is composed of multiple cells.
Oracle, in addition to offering PCI-card-based flash, manufacturers the Sun Storage F5100 Flash Array. The company says its product, which offers up to 2TB of storage, is the first solid-state flash storage. PureStorage with their 100 TB FlashArray is no doubt a takeover target for one of the largest companies not yet offering that capability.