In every engineer’s life, there comes a time when your company decides it’s time to choose a new web host. This process can go smoothly, or you could crash and burn. The difference in the outcomes often comes down to: IOPS.
What are IOPS?
So what are IOPS? IOPS stands for Input/Output operations per second. This is an allowed value pre-determined by your webhost, which controls how many Input/Output operations are allowed at once on your server. After the threshold is reached, the host may begin throttling these operations, causing requests and processes to queue up. This in turn causes sleep-state processes, which inflates your server load more and more, until the backlog queue of requests finally completes. The processes left waiting in this time are affected by “IOWait.”
So why are IOPS important?
With that in mind, it’s first important to understand how many IOPS your site really needs. Start by getting some stats from your current environment. How long does it take your current server to process requests? How many CPU cores and how much Memory is allocated on your current environment? At your daily peak for CPU load, how many active processes were running and how fast were they? What is the ratio of disk reads to disk writes?
What IOPS benchmarks are important?
Second, don’t take the IOPS metrics different companies boast about too seriously. IOPS can vary drastically depending on the type of operation, size of the server block, number of requests, and weight of those requests. It would be easy for a vendor to falsely inflate the IOPS their systems can handle by showing a dedicated block with lightweight reads and writes. It’s important to ask about how the benchmarks were made. What was the read/write ratio? Were there other tenants on the disk? Is there a set point at which requests are throttled?
It might be more appropriate to develop a test instance of one of your heavier-trafficked sites on a new web host, and perform load testing to see how the type of traffic your site normally experiences performs on the new environment. The more specific to your own needs the testing can be, the better. Be sure to check with the vendor on their policies for load testing before getting started.