Start-up releases fast, efficient enterprise-class SSDs

Pliant claims that its solid state drives offer twice the performance of competitors

Pliant Technology has released its first series of enterprise-class solid state disk (SSD) drives based on a proprietary ASIC design. The company claims it can handle – without using any cache – more than twice the input/output operations per second (IOPS) as the top competitive drives.

The first two enterprise flash drive (EFDs), the EFD LS and EFD LB models, are 3.5-inch and 2.5-inch drives that can produce up to 180,000 IOPS and 140,000 IOPS respectively. The 3.5-inch drive can produce up to 500MB/sec sustained read or 320MB/sec write rates and the 2.5-inch up to 420MB/sec read and 220MB/sec write rates, Pliant says.

"Put it on a log application and write to it as hard as you want for five years – it will run 24/7 for at least that long," says Greg Goelz, vice president of marketing at the three-year-old startup.

Pliant also claims there is no limit to the number of writes that can be performed to the drive and that it will work without slowdown for at least five years. The drives are aimed at equipment manufacturers such as EMC, Hewlett-Packard, Hitachi Data Systems and Sun Microsystems, the company says.

"They're able to claim some pretty solid performance numbers on read and writes and they're also able to claim unlimited program and erase [write/erase] cycles," says Joseph Unsworth, research director for NAND flash semi-conductors at Gartner. "That is big. In an enterprise environment, that is one of the major concerns: The wear out of the SSD."

Most enterprise-class SSD companies today use Fibre Channel connectivity. Pliant's first products use serial-attached SCSI (SAS), which most industry observers believe is the interconnect of the future for servers and storage arrays. "You don't want to saturate your [server] CPU cores and then find out we have this great SSD, but the bottleneck is now the interface," Unsworth says. "It's all about speed."

SAS currently supports 6Gbit/sec data transfer speeds and its roadmap indicates 12Gbit/sec rate by by 2012. Fibre Channel drives are currently capable of 4Gbit/sec data transfer speeds, and while Fibre Channel switches and interface cards are now emerging with 8Gbit/sec speeds. SAS is eclipsing those speeds at the device level.

"Six gigabit SAS in terms of data throughput is going to be the performance leader," says Jeff Janukowicz, a flash memory analyst with IDC in Framingham, Massachusetts. STEC, the top provider today of enterprise-class SSDs, recently announced its own SAS model. But even that next-generation product produces a maximum of 80,000 IOPS compared with Pliant's 180,000 IOPS.

Pliant's SSD controller architecture is not vastly different from those of other high-end SSD manufacturers. It has 12 independent I/O channels to interleaved single level cell (SLC) NAND flash chips from Samsung. The drives are configured as RAID 0 for increased performance and the controller.

Most enterprise-class SSDs today also use a general purpose field programmable gate array (FPGA) controllers as opposed to Pliant's custom controller, which is programmed specifically to address SSD issues, such as wear leveling (spreading writes more evenly throughout the memory) and write amplification (reducing the number of operations required for a write), according to analysts.

Also unique to Pliant's controller is the use of a triple redundancy error correction code algorithm to ensure that meta data – which is used to locate data on the drive – is saved even if two copies of it become corrupted. Also, the lack of any DRAM cache, which can store data writes more quickly, laying them down on the NAND flash chips during non-peak performance periods, is also unique to Pliant's enterprise-class product.

Some of today's more popular server-class SSDs, like those from Intel, use serial ATA interfaces, which has a half-duplex interface as opposed to SAS, which like Fibre Channel, is full duplex. The difference between the two is that full duplex is dual ported, allowing for reads and writes at the same time. Single-port half-duplex allows for one or the other.

Pliant, based in Milpitas, California, released its new SSDs for beta testing last year and plans to make them generally available later this month. The company raised US$15 million in Series C funding in March, which was used to ramp up production of the SSDs, the company says.

"I think with Pliant's announcement we are starting to see some of the true promises of SSD coming to market," Janukowicz says. "A lot of these applications are demanding, mission critical, 24/7 applications and they require high reliability, efficiency and predictable performance. And, based on Pliant's claims, they seem to have addressed many of those important issues."

The company refused to release a suggested retail price for the drives. However, it did note that the drives will be more expensive than Intel's X25-E SSD , which sells for $780 for a 64GB SATA model, and less expensive than STECs Zeus SSD , which sells for about $6000 for a 73GB Fibre Channel model.

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