# Overprovisioned managed disk for VM limits | Cloud Efficiency Hub Canonical: https://www.pointfive.co/efficiency-hub/inefficiencies/overprovisioned-managed-disk-for-vm-limits Each Azure VM size has a defined limit for total disk IOPS and throughput. By: Balazs Engedi Updated: 2026-09-28 [Cloud Efficiency Hub](https://www.pointfive.co/efficiency-hub) # Overprovisioned Managed Disk for VM Limits The short version Each Azure VM size has a defined limit for total disk IOPS and throughput. [Balazs Engedi](https://www.linkedin.com/in/engedib/) FinOps Specialist @ KPN Azure service [Azure Managed Disks](https://www.pointfive.co/efficiency-hub/cloud-services/azure-managed-disks) Category [Storage](https://www.pointfive.co/efficiency-hub/service-category/storage) Reference CER-0122 Type Overprovisioned Resource ## Explanation Why the waste happens and who it affects. When high-performance disks (e.g., Premium SSDs with high IOPS capacity) are attached to low-tier VMs, the disk's performance capabilities may exceed what the VM can consume. This results in paying for performance that the VM cannot access. For example, attaching a large Premium SSD to a B-series VM will not provide the expected performance because the VM cannot deliver that level of throughput. Without aligning disk selection with VM limits, organizations incur unnecessary storage costs with no corresponding performance benefit. ## Billing model The pricing dimensions that drive this cost. Azure Managed Disks are billed based on: - Provisioned capacity (GB/month) - Disk type (Premium, Standard SSD, etc.) - Provisioned performance (IOPS and MBps), where applicable However, the maximum usable IOPS and throughput is also capped by the VM size - regardless of what the disk can deliver. ## How to detect 4 checks to find it in your estate. - Compare attached disk performance (IOPS and MBps) against the maximum supported by the associated VM size - Identify cases where disk capabilities exceed what the VM can deliver - Review whether performance tier (e.g., Premium SSD) is justified for the workload - Consult VM and disk documentation to validate the effective throughput bottleneck ## How to fix 3 ways to remove the waste. - Match disk performance to the VM's limits: for Premium SSD v2 and Ultra Disk, lower provisioned IOPS and throughput in place; for Premium SSD, return any raised performance tier to the baseline tier, or migrate data to a new, smaller disk, since managed disks cannot be shrunk in place - Downgrade to lower disk tiers (e.g., Premium SSD to Standard SSD) when full performance is not needed - Establish guardrails to ensure disk and VM configurations are aligned during provisioning and resizing events ## Documentation Vendor references for pricing and configuration. - [Azure VM Sizes and IOPS Limits learn.microsoft.com](https://learn.microsoft.com/en-us/azure/virtual-machines/sizes) - [Azure Managed Disk Types and Performance learn.microsoft.com](https://learn.microsoft.com/en-us/azure/virtual-machines/disks-types) - [Performance tiers for Azure Premium SSD managed disks learn.microsoft.com](https://learn.microsoft.com/en-us/azure/virtual-machines/disks-change-performance) ## Related inefficiencies [Browse the library](https://www.pointfive.co/efficiency-hub) - Azure Managed Disks CER-0338 ### [Underutilized Azure Managed Disk Reservations](https://www.pointfive.co/efficiency-hub/inefficiencies/underutilized-azure-managed-disk-reservations) Azure Managed Disk reservations allow organizations to pre-purchase Premium SSD capacity at a discounted rate by committing to a one-year term. However, these reservations operate on a strict use-it-or-lose-it basis - if reserved disk... Storage - Azure Managed Disks CER-0094 ### [Missing Performance Plus on Eligible Managed Disks](https://www.pointfive.co/efficiency-hub/inefficiencies/missing-performance-plus-on-eligible-managed-disks) For Premium SSD, Standard SSD, and Standard HDD managed disks 513 GiB or larger, Azure now offers the option to enable Performance Plus - unlocking higher IOPS and MBps at no extra cost. Many environments that previously required custom... Storage - Azure Managed Disks CER-0121 ### [Outdated and Expensive Premium SSD Disk](https://www.pointfive.co/efficiency-hub/inefficiencies/outdated-and-expensive-premium-ssd-disk) Workloads using legacy Premium SSD managed disks may be eligible for migration to Premium SSD v2, which delivers equivalent or improved performance characteristics at a lower cost. Premium SSD v2 decouples disk size from performance... Storage --- Source: the public page above. Product screenshots and illustrative interfaces are examples, not live customer data.