Intel On Enterprise Storage: No More SLC; Meet HET MLC
You'll find some of the highest-end computer hardware in the largest data centers and supercomputing labs; stuff that would blow your mind. When it comes to the high-performance storage in those environments, SSDs based on single-level cell (SLC) memory elements are often favored for their great performance, power, and reliability characteristics.
In the early days of solid-state storage, multi-level cell (MLC) NAND SLC-based SSDs were deemed unsuitable for the write-intensive nature of many server workloads. The technology weathers fewer program and erase (P/E) cycles before deteriorating. Moreover, MLC achieves slower write speeds than SLC-based cells. And, in the process, MLC memory uses more power (an important consideration in a data center potentially playing host to thousands of drives).
As a result, many IT managers look to SLC-based drives for applications where data security and speed are of the utmost importance. Specifically, Intel's X25-E (first reviewed back in 2009: Intel’s X25-E SSD Walks All Over The Competition) is the benchmark by which other enterprise-class SSDs are measured.
There are a couple of problems, though. First, as its name suggests, an SLC memory cell only stores one bit of data. Compute-quality MLC stores two. Right off the bat, you can see that multi-level cell technology is what facilitates the higher capacities many SSDs enjoy today. Intel's X25-E, in comparison, topped out at 64 GB. The other issue is price. That same 64 GB flagship sells for as much as $800, more than $12 per gigabyte of storage.
Clearly, if a manufacturer could figure out a way to push the benefits of MLC-based NAND into the enterprise without compromising data integrity, there would at least be a compelling reason to start slinging larger SSDs together in RAID, or using them singularly as caching devices in a tiered storage subsystem, right?
Well, Intel certainly thinks so. The company is discontinuing the X25-E altogether in favor of a new SSD 710, representing a shift from expensive SLC to more accessible MLC memory.
Despite the fact that Intel's new data center drive takes the MLC route, the company says it delivers a different experience than the mainstream SSD 320. The NAND found in Intel's new enterprise SSD is dubbed "High Endurance Technology (HET) MLC", which tries to balance the capacity benefits of MLC and write endurance of SLC memory.
The move away from SLC naturally involves some compromise. However, from a big-picture approach, it makes sense. When you combine the technical barriers to SLC production and factor in economies of scale, at the same density, SLC NAND commands a price premium 4x higher than MLC, according to data from iSuppli. An MLC-based drive is going to be much more accessible to cost-conscious SMBs and larger data centers alike.
|Cost||Market Price (Debut)||Price Per GB|
|Intel X25-E 32 GB||$460||$14.38|
|Intel X25-E 64 GB||$900||$14.06|
|Intel 710 SSD 100 GB||$679||$6.79|
|Intel 710 SSD 200 GB||$1299||$6.50|
|Intel 710 SSD 300 GB||$1999||$6.63|
Oh yeah. Look at the difference in price per gigabyte. The X25-E debuted at about $14/GB. More than two years later, just before Intel announced it was discontinuing the X25-E, it had only dropped to about $11/GB. That's still a 40% price premium over this new SSD 710, though. But there's more to the story than just dollars and cents.
Consumer-oriented SSDs are still hovering near $2/GB. So, an MLC-based SSD priced at $6.50/GB should still rightly raise some eyebrows. However, the HET MLC found in Intel's SSD 710 is purported to offer write endurance 30 times greater than the cheaper consumer-grade MLC. So, if we assume that 25 nm MLC NAND is rated at 3000 P/E cycles, HET MLC should come close to 90 000 cycles. That SLC-like write endurance rating is intended to assuage the fear of IT managers now unable to purchase the X25-E and faced with SSD 710. A substantially-lower price per gigabyte, meanwhile, is designed to attract the contingent of folks stuck using magnetic storage because they couldn't stomach the premium on SLC memory for their mission-critical data.