Pliant trades off firmware complexity against MLC NAND Flash capacity in enterprise SSDs

The multiplicative storage capacity of MLC (multi-level cell) NAND Flash is a siren song to SSD manufacturers but the added storage has a price in terms of access speed and, perhaps more important, data reliability. When you’re storing two or more bits in a NAND Flash cell, there will inevitably be more data errors--which may sound like a really bad thing but it’s not if you have the right perspective. The HDD industry has had the right perspective for decades. Hard-drive engineers know they will be working with imperfect storage media and they have installed the necessary error-management technologies to turn faulty storage into perfect storage. Solid-state-drive engineers are only now really coming to grips with the same situation. After having gone through the designs of the first few generations, SSD design teams are now implementing more complex error-management and wear-leveling algorithms and running them on faster embedded processors to compensate for the new issues cropping up with the use of MLC and TLC (three-level cell) NAND Flash.

Case in point: Pliant Technology, which has just introduced a line of enterprise SSDs with SAS interfaces based on MLC NAND Flash. Pliant based its new new Lightning LB 200M (200Mbytes) and Lightning LB 400M (400Mbytes) enterprise flash drives on MLC NAND Flash memory devices coupled with a new controller design and software that can meet data center requirements for storage capacity and integrity, per an article in Computerworld, written by Lucas Mearian.

However, faster processors and better algorithms cannot compensate for the speed loss when switching from SLC (single-level cell) NAND Flash memory to MLC devices. Pliant’s new 2.5-inch LB-series SSDs can achieve up to 10,000 IOPS, but that’s compared to 35,000 IOPS for the company’s SLC-based LS-series SSDs. But the LS series is currently limited to 150Gbytes in the 2.5-inch format compared to the 400Mbyte maximum capacity of the LB series of 2.5-inch SSDs.

Pliant Technology press release here.