What Is Short Stroking And Why Should You Care?

As the major storage vendors start rolling out the Solid State Disk solutions, you're going to hear a term that you may not have heard for a while, if ever; short stroking. Short stroking a drive is a method to format a drive so that only the outer sectors of the disk platter are used to store data. This practice is done in I/O-intensive environments to increase performance.What does this have to do with SSD's? Short stroking a drive will deliver excellent performance but is very costly. In high-performance environments, this short stroking is done on high-RPM (15k) and low-capacity drives. Not only are they expensive because of their high speed, but also because they are lower capacity per drive. This is obviously compounded because you further limit capacity due to the short stroke format. Then in almost every situation, these applications are deployed across a very large number of these drives that have been short stroked; 30 to 40 isn't uncommon, and I have seen as high as 300.

If you do the math, this gets very expensive very fast, but I can almost guarantee that every one of these solutions are more cost justified than any other solution in the data center. Why? Most of the applications that need this type of performance are the heart and soul of the organization; they are specifically involved in revenue generation and can almost always track to the dollar what the extra effort in performance makes for the company. That said, no IT professional gets excited about buying huge quantities of the most expensive drives available and only formatting them to less than half of their actual capacity.

The solution from torage manufacturers and the specialized SSD suppliers is to offer SSD drives and they are often the perfect solution. As detailed in my last post, there are different types and you need to select the right type of SSD for you. There is, however, an in-between step, offered by some of the storage virtualization solution providers ,such as 3PAR and Hewlett-Packard; Wide striping.

Wide striping scatters chunks of the storage across all the available drives in the system. While you still may purchase a bunch of 15K drives for performance, those drives do not have to be short stroked. The data is scattered across them and, in the case of 3PAR, their systems will even make sure that the most I/O intensive blocks of data stay on the outer sector of the drives platters. The big gain, however, is that the inner sectors can still be used for other data where performance isn't as critical. That said, remember these are still 15K drives, so it will still be fast compared with a 10K drive.

We always talk about SSD's being Tier 0, but there are a lot of performance options between Tier 1 and Tier 0. Short stroking is one example and wide striping is another, and possibly a more palatable one. Even with SSD's, there are performance differences between Flash-based and DRAM-based solutions. SSD's are fantastic performance enhancers, but not every application needs them or can even take advantage of their performance.

Performance is a never-ending chase. The best advice here is to make sure you understand not only all the performance options available to you, but also the performance requirements and capabilities of the applications that you're concerned with.

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Subscribe to our RSS feed. George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.