Pliant adds MLC SSDs to Lightning lineup

By Dave Simpson

Augmenting its family of solid-state disk (SSD) drives based on single-level cell (SLC) NAND flash, Pliant Technology today announced two SSDs based on the less expensive multi-level cell (MLC) NAND flash technology.

The 2.5-inch 200GB Lightning LB 200M and 400GB LB 400M Enterprise Flash Drives (EFDs) are currently sampling to Pliant’s OEM customers, with availability from the company’s resellers expected next month. Pliant did not release pricing information, which is up to its channel partners and OEMs, but cost-per-GB pricing for the MLC SSDs is expected to be about half of the company’s SLC-based SSDs.

Unlike most SSDs on the market, Pliant’s drives are based on SAS (3Gbps) interfaces, as opposed to the more common Fibre Channel or SATA interfaces.

In general, MLC has higher capacity and lower cost than SLC flash, but MLC also has lower performance and endurance (reliability) characteristics.

Greg Goelz, Pliant’s vice president of marketing says that, in general, SLC flash delivers 3X the performance of MLC flash, yet at about twice the cost. In terms of reliability, Pliant specifies a five-year lifecycle for its MLC-based SSDs, compared to a seven-year lifecycle for its SLC NAND SSDs.

Unlike most SSDs, Pliant’s EFD drives do not include a write cache.

“To make write caches non-volatile, most vendors use batteries or supercapacitors,” says Goelz, “and time and temperature are enemies of those technologies. As such, write caches are not good for data reliability,” he claims.

For increased performance without using a write cache, Pliant relies on a combination of data management software, bandwidth, and custom ASICs on its controllers.

The company claims sustained performance of more than 10,000 I/Os per second (IOPS) on the LB 400M SSD and 8,000 IOPS on the LB 200M SSD with a block size of 4KB and a 70/30 read/write mix.

With 8KB blocks, read/write ratios ranging from 90/10 to 60/40 and a queue depth of 64, the company claims more than 6,500 IOPS on the LB 200M and 7,500 IOPS on the LB 400M.

And Pliant specifies a sustained read/write data transfer rate of more than 240/100MBps for the LB 200M and 270/100MBps on the LB 400M.

Idle power consumption for both devices is 3.9 watts, and typical power consumption is 4.9 watts for the LB 200M and 5.4 watts for the LB 400M.

Endurance-enhancing features include background Patrol Read (which minimizes the “read disturbs” effect), Memory Reclaim, extended ECC, and support for the T10 Data Integrity Field (DIF) standard. The company claims unlimited read/write endurance, and an MTBF of two million hours.

Related articles:

Pliant delivers EFD SSD drive

MLC vs. SLC flash for enterprise SSDs

Does MLC flash belong in enterprise SSDs?

This article was originally published on September 08, 2010