In SSDs, IOPS Is King


Those of you evaluating solid state disks (SSDs) for the enterprise already know that performance is not measured in capacity as with traditional hard disks. The main benefit of the SSD is speed. So it's no surprise that the newest devices about to hit the market tout IOPS over GBs.


But one of the things to keep in mind, according to STEC's Mark Moshayedi and Patrick Wilkison, is that SSDs are only beneficial in situations where they can produce a significant cost savings over existing architectures.


As an example, the pair cite server applications that currently require a large number of fast hard disk drives, typically Fibre Channel or SAS drives spinning at 15,000 rpm. To get the I/O performance up, many systems utilize only the outside ring of the disk platter as a means to limit the movement of the spindle. The drawback here is that it dramatically cuts down on capacity, to the point that a single SSD could replace upwards of 30 high-speed HDDs. That means some serious coin not only for the drives, but the cost of racks, enclosures, controllers, switches and power.


But when it comes to speed, whose SSD is the fastest in the land? Micron is making a run at the title, having recently demonstrated an experimental device said to offer throughput of 1 GBps and upwards of 200,000 IOPS. The company has a dual SSD card with 16 flash channels that ties directly to a PCI Express slot, avoiding the slower SAS or SATA interfaces. The device is said to achieve nearly 160,000 random reads per second with files ranging from 2 KB to 2 MB.


Micron is also working closely with Intel on a new generation of 34 nm NAND flash memory chips, possibly a key breakthrough in the pursuit of higher capacities. To date, narrower flash geometries have been inherently unstable, making them unsuitable for embedded devices, let alone mission-critical enterprise applications.


Another name to watch is SanDisk, which recently released the Extreme Flash File System (ExtremeFSS) as a means to boost random write speeds. The company is hinting at another breakthrough possibly next year that should put random write on par with sequential write, overcoming one of the chief drawbacks of SSDs compared to HDDs. The company is also toying with 3- and 4-bit multi-level cell technology as a means to boost capacity.


FusionIO, however, is laying claim to the world's fastest available SSD, the ioDrive.


The target for most SSD vendors are the high-speed hard disks in the enterprise, but hardly anyone is talking about the end of HDDs. Mixed environments will likely be the order of the day going forward.