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Solid-state drives (SSD) have been one of the hottest storage technologies of 2008, beginning with the January announcement by EMC that it would support flash drives with SATA interfaces in its Symmetrix disk arrays. Since then, more storage vendors have vowed support for SSDs, although many products won't hit the market until late this year or early 2009.
There are dozens of SSD manufacturers, but only some are specifically targeting the enterprise SSD space, which has different requirements for flash design than consumer technology. The most common design differentiation between enterprise SSDs and consumer SSDs, which might appear in your iPod, may be single-level cell (SLC) versus multilevel cell (MLC) technology. Enterprise drives use SLC designs for better endurance and data integrity. All flash drives today have a finite tolerance for write/erase cycles.
A few SSD makers have announced products specifically meant for that enterprise SLC space. Stec was the first with its design win for EMC Symmetrix arrays.
Samsung was the next to be publicly revealed in partnership with Sun Microsystems. Sun and Samsung claim that they worked together to make SLC flash more durable through methods, such as reserving flash blocks to extend write endurance life and (proprietary) changes to the recipe for the flash material itself.
DRAM manufacturer Micron launched its first generation of SSDs for enterprise servers in August. Micron claims its RealSSD P200 drives use DRAM cache to efficiently wear-level the flash memory cells.
Intel said that it will also ship enterprise SSDs by year's end. The chipmaker said it had engineered its X25 E -- the enterprise version of its SSD -- with 10 I/O channels to each die. This, it said, would boost performance. To boost endurance, wear-leveling algorithms would cut down on "write amplification" or the number of writes to the flash dies needed to commit a write from the host to the medium.
Fusion-IO, which came out of stealth earlier this year with its own enterprise SSDs, announced in August full-chip redundancy on its ioDrive, bringing RAID-class redundancy using "flashback" protection down to the card level. The company integrated a dedicated NAND flash chip on its PCIe card, which serves as a XOR parity chip, eliminating data loss due to chip failures and extending the card's lifetime.
According to IDC, SSD makers and storage system vendors will continue to build better mousetraps over the next few years. The analyst firm is sticking with its earlier forecast that deployment of SSDs in enterprise computing will pick up by 2010, and that enterprise computing applications will grow from 12% of SSD revenue in 2007 to more than 50% by 2011. But, a report released in July suggests that enterprise operating systems and storage arrays will need some level of redesign with SSDs in mind in order to take advantage of the IOPS they offer.
Storage and system vendors debate best place for SSDs
Currently shipping with disk arrays
EMC Symmetrix DMX-4 high-end disk arrays have supported SSDs from Stec since March. EMC has integrated the drives with management, provisioning and replication software used for Symmetrix systems so that putting data on the drives and migrating it off is no different than with a mechanical drive. In August, EMC announced it will also support solid-state drives in Clariion arrays next year.
NetApp Performance Acceleration Modules (PAM) and SA2000, SA300 and SA600 storage acceleration cards use memory to speed performance. PAM is a separate device, while the cards can be added to the FAS2000, FAS3000 and FAS6100 filers, respectively. "Flash technology employed in a high-performance read cache is the architecture chosen by NetApp in its first-generation solid-state offering," said Patrick Rogers, vice president solutions marketing. NetApp is currently shipping a plug-in DRAM cache card and will offer a version using flash chips next year.
Xiotech Magnitude 3D arrays currently support SSDs and support for SSDs is also on the roadmap for the company's newer self-healing Emprise arrays.
Texas Memory Systems, the doyen of solid-state vendors, has added flash SSD backup capacity to its DRAM-based RamSan for persistent data storage.
BlueArc has announced interoperability between its Titan 2000 and Titan 3000 storage systems and Texas Memory Systems' RamSan-400.
Solid Data offers a standalone array, called the StorageSPIRE SSD Array, in 500 GB to 1 TB capacity, connected by 4 Gbps Fibre Channel. Violin Memory makes a similar standalone product that uses flash memory or DRAM and offers RAID data protection among the solid-state devices.
The server side
Some companies, like Hewlett-Packard, Fujitsu and Pillar Data Systems, argue that the best place to take advantage of SSD performance is directly attached to the server's PCIe bus, rather than behind a network and storage controller many times slower than the drive itself. HP has qualified Samsung SSDs for its ProLiant BL2x220c, BL260c and BL495c servers, though it will also offer SSD support in its rebranded version of Hitachi Data Systems' USP-V array, the XP24000, when it becomes available late this year or early next year.
IBM is also putting its solid-state drives from Fusion-IO closer to the server with plans to incorporate the technology into its SAN Volume Controller (SVC) network storage virtualization device, which is itself a server that attaches to the SAN switch. IBM argues this is a "best of both worlds" approach to getting the SSD out from behind the storage controller but integrating it with the storage infrastructure. Like HP, IBM also supports SSDs in multiple server models.
On the roadmap
For every storage vendor currently shipping product, there are several more whose public plans include support for the devices by the end of 2008 or early 2009. Such companies include 3PAR, Dell/EqualLogic, Compellent, HDS and Sun.