The term “SSD” has usually been a mnemonic for “solid-state disk” drives, as in flash memory modules that are put into traditional disk drive form-factor packages. This format is perhaps the easiest to integrate into an existing storage environment, either as replacement server-based disk drive(s) or for use in an external disk array. But this packaging includes a SAS or SATA interface for each SSD itself and for legacy external arrays and involves running solid-state storage devices through a controller designed to support spinning disk. New, dedicated SSD arrays are available that integrate the flash memory modules directly onto cards inside the array and skip the disk form-factor package altogether. Storage Switzerland was briefed by two of these companies at the recent Flash Memory Summit.
Violin Memory’s Memory Array supports up to 10 TB of single-level cell (SLC) flash on hot-swappable, internal circuit cards the company calls “VIMMs” in a 3U enclosure. Card-mounted flash provides better density than drive form-factor SSDs, lowering the cost per gigabyte and providing better performance through the elimination of the SAS or SATA protocol. Putting more flash modules together on each card also improves the write performance, since writes can be spread over more flash modules and overhead can be done more efficiently.
Nimbus Data Systems’ dedicated flash array also puts flash modules onto hot-swappable circuit cards, or “flash blades.” A 2U array holds 24 of these blades and provides 2.5 TB of capacity. Nimbus’ HALO operating system includes storage features like snapshots and replication but also deduplication and thin provisioning. These capabilities give the system a much larger effective capacity and lower its cost per gigabyte.
Solid-state storage is moving into the dedicated array space with some compelling capabilities and price/performance numbers. These “pure flash” SSD arrays deserve a closer look by any VAR that’s serious about storage.
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