August 23, 2011
Storage maker Texas Memory Systems (TMS) has launched its first enterprise multi-level cell (eMLC) flash-based product, expanding the company's market reach into the tier 1 storage arena. The company's 10 TB RamSan 810 product delivers eMLC-based storage at about half the cost of conventional flash-based enterprise storage. The move comes as more solid state disk (SSD) vendors are using the technology to challenge disk-based systems on performance-demanding applications.
The oldest SSD vendor in the industry, TMS released its first solid-state storage product back in 1978. That was a RAM disk-based system, almost thirty years before the advent of enterprise-worthy NAND flash. The company still sells RAM-based storage, as well as a RAM-NAND hybrid offering. But their main product set is now centered on flash memory, which comes in both rackmount and PCIe versions. Until this week, all of those employed the single-level cell (SLC) variety, the traditional flash technology for enterprise SSDs.
SLC offers just half the storage density of vanilla MLC, but is far more robust, offering error rates two orders of magnitude better. The relative newcomer is eMLC, a variant of MLC with its same storage density but with much improved write endurance. For eMLC, native error rates are some between those of MLC and SLC, but can be compensated for by using more aggressive ECC schemes in the flash controller. The big advantage for eMLC is cost, which is more expensive than MLC, but significantly less so than SLC.
As such, eMLC has become an enabling technology for flash vendors looking to go after the disk-dominated primary storage market. When compared against high-performance 15K disks, eMLC flash-based storage is on par, cost-wise, with regard to capacity and is far superior in performance, power consumption, and density. Even when compared with cheaper high-capacity disks, the cost per GB of eMLC may be higher, but the cost per bandwidth is lower. As long as capacity requirements are not extreme, those characteristics makes the technology a nice fit for tier 1 storage in the datacenter.
TMS is certainly positioning the 810 as an entry point into that market, especially for those applications that don't need a lot of write endurance (i.e., are read-dominated), but are performance limited. It's also targeted to applications that need fast random access to relatively large data sets, but which don't fit in main memory. "We find that the 10 TB capacity hits the sweet spot for a lot of databases, which are usually a couple of terabytes in size." says Erik Eyberg, Senior Analyst at TMS.
That encompasses a lot of mainstream datacenter applications like content distribution and data warehousing. It also includes a number of HPC applications, where irregular access to large data sets results in performance-sapping bottlenecks. This is particularly true in workloads like Reverse Time Migration, in which the entire set of seismic data has to be accessed randomly.
In the TMS portfolio, the 810 represents the eMLC-based alternative to the company's SLC-based RamSan 710, a 5 TB SSD system aimed small SAN installations. Although both come in the same 1U box, thanks to the denser eMLC chips, the 810 has twice the capacity at the same price. Performance is diminished, but not dramatically: 320K IOPS (read and write) and up to 4 GB/second of bandwidth for the 810 versus 400K IOPS and 5GB/second for the 710.
Error correction is a little tougher on the eMLC technology, so TMS had to tweak the software on their standard flash controller to add extra ECC bits. The company is touting a 10-year lifetime on the 810 boxes with write rates of 600 MB/second, which is equivalent of writing the entire flash memory five times per day. From the application's point of view though, the 810 behaves much like the 710, with the exception of slightly less performance. Both the 710 and 810 are equipped with 8 Gbps Fibre Channel and 40 Gbps (QDR) InfiniBand ports, the latter for HPC cluster connectivity.
According to Jamon Bowen, director of sales engineering at TMS, the choice will basically come down to how much data needs to be sped up. "If somebody is looking to do metadata acceleration inside their file system, they'll probably look at our SLC product," says Bowen. "If they're trying to do the actual data acceleration, that's when they'll look at the eMLC."
TMS joins companies such as Nimbus Data Systems, SMART Modular Technologies and OCZ Technology Group, who are also offering eMLC-based SSDs. Nimbus, in particular, has a complete product set built on eMLC flash, and recently jacked up the performance on the entire S-Class line.
According to Bowen though, the 810 won't go head-to-head with the Nimbus offerings, since that company wraps a complete NAS/SAN storage management suite around their system. The RamSan 810 is strictly a hardware play, relying on an external file system or third-party utilities to provide storage management. For the HPC community such management is rarely a concern, says Bowen, since clustered file system, such as GPFS, are usually layered on top of the storage.
What TMS is selling in the 810 is an exceptionally fast virtual disk that plugs into a namespace. As such, the company sees their main competition as other disk-based SAN vendors like NetApp and EMC. "If it's a performance-based play, we'll do very well." says Bowen.
The new eMLC-based systems will go for around $13.00/GB (which is pretty much on par with $12.65/GB that Nimbus quotes for its S-class gear). Given that, a 420 TB rack of 810 boxes will cost about $5,460,000 while delivering 140 GB/second of bandwidth. Some beta customers have expressed interest in doing deployments at this scale, particularly those with price-sensitive, low-write workloads.
"You can really talk about petabyte-scale SSDs in a viable way," says Bowen. "It's not out of the price range of a large application and it's not that big -- just two racks."
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