AWS Certified Solutions Architect Associate Test 7

Several factors can affect the performance of Amazon EBS volumes, such as instance configuration,I/O characteristics, workload demand, and storage configuration. IOPS are input/output operationsper second. Amazon EBS measures each I/O operation per second (that is 256 KB or smaller) as oneIOPS. I/O operations that are larger than 256 KB are counted in 256 KB capacity units.
For example, a 1,024 KB I/O operation would count as 4 IOPS. When you provision a 4,000 IOPSvolume and attach it to an EBS-optimized instance that can provide the necessary bandwidth, youcan transfer up to 4,000 chunks of data per second (provided that the I/O does not exceed the 128MB/s per volume throughput limit of General Purpose (SSD) and Provisioned IOPS (SSD) volumes).
Reference: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSPerformance.html