When do you need Flash Storage?

Gerard Almon – 17 September 2013

I am frequently asked to advise on storage configurations, and a common question is if we should add flash/SSD storage into a client configuration. The answer to this question is changing quite dramatically as the price of SSDs come down and capacities grow. In most configurations, if you are really serious about the question then the answer is probably “Can you give a reason why not to run SSD?”

Although we’ve seen improved performance using SSDs for almost every workload during lab testing, there are some workloads that perform especially well with SSD technology. Database workloads work well with SSDs not only because of the higher raw performance of SSDs, but because of the reduced latency. We’ve seen significant performance improvements when using SSDs for primary storage. Placing the application data entirely on flash for primary storage will prove enormous benefits immediately for that application. We’ve seen performance improvements of 8x to 16x and more.

While an individual HDD can provide hundreds of IOPS, SSDs typically provide thousands or tens of thousands of IOPS with a single device. In some online transaction processing (OLTP) application environments, including database and Web server environments, short response times are often critical. A transaction may require many successive queries to a database, where each query depends on answers returned from the previous query. In those cases, user response times are entirely dependent on how quickly storage can return answers to the entire series of queries. In most cases, we’ve seen sub-millisecond latency using SSD technology, which may be more important than the raw IOPS or throughput performance.

If you understand your workload profile, a good fit for SSD would be any application that is read-intensive and random in nature, especially when using small block transfers (Such as DB2, Oracle, SQL Server) . A workload that use large, sequential writes such as backups or media streaming usually don’t quantify running on SSD.

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