Tech Notes

According to searchstorage.com, there are over 400 companies designing and marketing solid state disks today.  Wow.  And according to the folks at the InfoPro, a service of 451 Research, which provides insight based on one-on-one, in-depth interviews with a proprietary network of the world’s largest buyers and users of IT, auto-tiering is perhaps the hottest storage technology today, as FC drives are being replaced with SSD and SAS blends (This figure came from their latest TIP Insight report.)  So I have to ask, are our performance problems over?  OK, it’s a rhetorical question.  But I have to laugh when someone points to IOPS or MB/s as their performance benchmark.  We’ve got plenty of examples where users were getting great utilization numbers, but their application owners were complaining of performance problems.  For example, in the time-correlated dashboard below, the top graph shows R/W MB/s and the middle graph shows application latency.  You probably can’t see the detail in this blog, but latency skyrockets from less than 25ms to over 150ms. Yet, MB/s doesn’t seem to be affected.

So, now that we know we have a problem, the solution is to apply SSD, right?  No.  Under normal circumstances, there is no performance problem and SSDs won’t make any difference.  The bottom graph shows a metric called Pending Exchanges.  In this case, there’s a very close correlation to how the HBA queue depths are set and the effect on application latency.  In this case, the customer adjusted the queue depth settings and the problem was remediated.

Maximizing application performance is one of IT’s most important tasks. The problem is that accurately identifying the root causes of poor performance is difficult, especially when the wrong metrics are used. This often leads to the assumption that storage subsystems are the bottleneck resulting in expensive upgrades, which still may not solve the problem. Through the use of a real-time, systems-level, Infrastructure Performance Management platform and metrics like transaction latency, IT can identify the real causes of application performance issues and fix those problems.  Sometimes, the best solution is to re-tier your application, applying SSD technologies.  But the best practice is to use the right tools to find out where these make sense, and when they don’t.

If you’d like to learn more about how to find the true cause of performance bottlenecks, call us, or call one of our resellers, and we’ll put you together with a performance specialist who can help you figure out when SSDs can help, and when they can’t.  Or check out this new report by Storage Switzerland, on “How do you know if you really need SSD”.