Let’s look at these metrics for a moment. If you've never studied the differences between SSDs and hard disk drives (HDDs) before, the comparisons can be striking. Although this data comes from a Samsung presentation on green SSDs and their benefits, the numbers correspond with our test results in prior articles.
We don’t want to comment on the gigabyte per watt section, as capacities are usually least relevant in this context. Yet we’d like to point out that SSDs of up to 512 GB per drive are available, basically matching 2.5” enterprise hard drives at 300 GB and 600 GB peak capacity points. In maximum I/O scenarios, where capacity hardly counts, a 64 GB SSD can even be cheaper than a comparable 73 GB enterprise HDD. As a result, SSDs are more relevant for I/O-intensive business applications than client PCs given their cost and performance attributes.
Capacities aside, you can’t really argue with SSDs' I/Os per dollar and I/Os per watt, as SSDs are typically much faster than hard drives while consuming a fraction of the power. Hard drives generally deliver between 100 and 400 I/O operations per second, depending on block size and random/sequential access. SSDs can hit five-digit I/O operations per second results.
In other words, SSD cost per gigabyte is comparable to HDDs while SSD cost per I/O trounces its magnetic competition, yielding a break-even on total cost of ownership. Effectively, you could deploy a single SSD to replace the I/O performance of dozens of hard drives or replace a certain amount of hard drives with SSDs, multiplying performance while still lowering power consumption. Also think about power and cooling requirements, which might decrease significantly thanks to a few SSDs potentially replacing an entire server rack.