Be sure to read through the previous post for a quick introduction of IOPS.

Suppose that you’re copying a 10GB file from one disk to another. Let us assume that the only bottleneck is the disks’ own IOPS, which in case is 120. We are also only focusing on the disk where the data is copied to and assume that the other disk has no IOPS limitation. Because we are writing about 10GB, the majority of the IOPS are going to be writes and not reads.

We will also assume that the disk has a block size of 64KB. In other words we are copying a maxium of 64KB of data in one operation (120 operations per second). That gives us a sustained throughput of about 7MB/s (120 * 64 * 1024). For a 10GB file, it would take about 1462 (10GB/7MB) seconds to copy the 10GB file.