When it comes to deploying SSDs for high reliability systems like servers, the choice has always been expensive SSDs that employ single-level cell (SLC) NAND flash memory. For a long time, the Intel X25-E Extreme SSD has been the preferred drive for data centers as reliability, endurance and performance are qualities native to SLC-based drives.
However, Intel is changing all that with the new Intel SSD 710 Series that uses Intel's latest 25nm MLC (multi-level cell) NAND flash memory with Intel High Endurance Technology (HET).
So what is it with MLC NAND that's so undesirable?
To understand why, one has to look at the fundamental construction between an MLC and SLC NAND flash memory. In an MLC NAND, a single memory cell can carry 2 bits of information as compared to SLC NAND. In other words, for the same amount of silicon real estate, you can theoretically double the amount of data stored in the NAND flash memory.
However, due to the complexity inherent in a multi-level cell structure, a lot of undesirable effects are introduced. Problems such as tunnel oxide degradation, cycling/programming precision errors, intrinsic charge loss, stress induced leakage current and defect failure due to large electric fields are some common problems found in typical MLC NAND.
However, with Intel's latest HET feature, a lot of the issues associated with MLC NAND flash memory were addressed through various enhancements in the process, binning and firmware. Thus, similar to producing high quality processors, similar tweaking to the manufacturing process as well as carefully picking premium NAND chips from the wafer is one technique that Intel employs to pick only the best and most stable memory chips for use in the high performance SSD. In terms of enhancements in the firmware, Intel added optimized error avoidance techniques, write amplification reduction algorithms and system-level error management. These new techniques, Intel claims, we able to solve the common reliability issues in MLC NAND and enable them to deliver the endurance required by enterprise-level systems.
Besides reliability enhancements, Intel also introduced several new features particularly for enterprise customers. These include enhanced power-loss data protection to reduce potential data loss during power failure; added data security with surplus NAND flash memory to provide system protection should a NAND die fail; Advanced Encryption Standard (AES) with 128-bit pre-configured encryption technology; and temperature monitoring and logging through internal temperature sensor.
As you can see in the table above, the new Intel SSD 710 Series now comes with much larger capacities, making them more suitable to today's data center usage. If you compare it with the SSD 320 Series, capacities are within the same range since both are based on the 25nm MLC technology. However, in terms of performance, the SSD 320 is slower in write speeds, simply because it's designed for PCs. Even its write endurance is vastly lower, in the range of TeraBytes as compared to enterprise grade drives like the X25-E and SSD 710 where it's in the range of PetaBytes. Still, one could see that the SSD 710 Series has slightly lower write endurance than the X25-E, but if you just compare between MLC drives, HET did help boost endurance to a very large degree.
Using MLC NAND flash memory in the new SSD 710 Series, Intel is able to provide a better dollar-per-GB value than its previous generation of Intel X25-E SSD. The new Intel 710 Series is priced at US$649 for the 100GB version, US$1,289 for 200GB and US$1,929 for 300GB (based on 1,000-unit quantities). These drives are also backed by a 3-year limited warranty.