SSD Performance and Cost

Before closing, let’s examine the performance and cost of modern SSDs, to better understand how they will likely be used in persistent storage systems. In both cases, we’ll compare to classic hard-disk drives (HDDs), and highlight the biggest differences between the two.

Performance

Unlike hard disk drives, flash-based SSDs have no mechanical components, and in fact are in many ways more similar to DRAM, in that they are “random access” devices. The biggest difference in performance, as compared to disk drives, is realized when performing random reads and writes. While a typical disk drive can only perform a few hundred random I/Os per second, SSDs can do much better. Here, we use some data from modern SSDs to see just how much better SSDs perform; we’re particularly interested in how well the FTLs hide the performance issues of the raw chips.

The table below shows some performance data for three different SSDs and one top-of-the-line hard drive; the data was taken from a few different online sources1-“The Seagate 600 and 600 Pro SSD Review” by Anand Lal Shimpi. AnandTech, May 7, 2013. Available: http://www.anandtech.com/show/6935/seagate-600-ssd-review. One of many SSD performance measurements available on the internet. Haven’t heard of the internet? No problem. Just go to your web browser and type “internet” into the search tool. You’ll be amazed at what you can learn. 2-“Performance Charts Hard Drives” by Tom’s Hardware. January 2015. Available here: http://www.tomshardware.com/charts/enterprise-hdd-charts. Yet another site with performance data, this time focusing on hard drives.. The left two columns show random I/O performance, and the right two columns sequential. The first three rows show data for three different SSDs (from Samsung, Seagate, and Intel), and the last row shows performance for a hard disk drive (or HDD), in this case, a Seagate high-end drive.