Find the real IOPS and throughput of an Azure disk layout after P-series limits, striping and the VM cap are applied.
On Premium SSD you cannot buy IOPS directly — performance is a fixed property of the snapped disk size, so a P30 gives 5,000 IOPS whether you need 500 or 50,000. Striping multiple disks multiplies the disk-side limit, but the VM's own uncached IOPS and throughput caps sit in front of it, and the smaller of the two is what the application sees. Most 'slow disk' tickets in Azure are actually VM-level caps, and adding a bigger disk to a small VM changes nothing; Premium SSD v2 and Ultra let you provision IOPS independently of size, which is often cheaper than buying capacity you do not need.
Azure Disk IOPS
Premium SSD IOPS and MB/s are fixed by the snapped P-series size; striped disks add up, then the VM's uncached limits cap the total: effective = min(disks × per-disk limit, VM limit).
Premium SSD IOPS and MB/s are fixed by the snapped P-series size; striped disks add up, then the VM's uncached limits cap the total: effective = min(disks × per-disk limit, VM limit). On Premium SSD you cannot buy IOPS directly — performance is a fixed property of the snapped disk size, so a P30 gives 5,000 IOPS whether you need 500 or 50,000. Striping multiple disks multiplies the disk-side limit, but the VM's own uncached IOPS and throughput caps sit in front of it, and the smaller of the two is what the application sees.
Most 'slow disk' tickets in Azure are actually VM-level caps, and adding a bigger disk to a small VM changes nothing; Premium SSD v2 and Ultra let you provision IOPS independently of size, which is often cheaper than buying capacity you do not need.
This calculator takes 7 inputs: Size of each disk, Disks striped together, Disk tier, Provisioned IOPS per disk (v2 / Ultra), Provisioned throughput per disk (v2 / Ultra), VM uncached IOPS limit, VM uncached throughput limit. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.