Q: Is the only difference between regular Azure storage and Azure Premium Storage for my IaaS virtual machine disks the higher IOPS?
A: Regular Azure storage has a certain IOPS limit for each virtual disk: 500 IOPS for a disk attached to a standard-tier virtual machine and 300 IOPS for a disk attached to a basic-tier virtual machine. You can verify this information in "Virtual Machine and Cloud Service Sizes for Azure." The key detail here is that this IOPS number is a maximum; the actual IOPS your disk receives will vary depending on other factors, such as other workloads on the host and storage. The IOPS number is a maximum rather than a predictable, expected number of IOPS.
Premium Azure storage features various tiers of disks with different IOPS values. However, these numbers aren't just maximums but are expected levels of performance. This means you can expect to see those levels of performance, which provides the predictability of performance that some workloads need. The three tiers of performance are listed in "Introducing Premium Storage: High-Performance Storage for Azure Virtual Machine Workloads."
- P10: 128GB, 500 IOPS with 100MB/sec throughput
- P20: 512GB, 2300 IOPS with 150MB/sec throughput
- P30: 1024GB, 5000 IOPS with 200MB/sec throughput
