LearnGlossary

What is Ultra Disk in Azure?

Updated 26 October 2026 · Published by Zoorik

Ultra Disk in Azure is the highest-performing type of Azure managed disk. You set its size, input/output operations per second (IOPS) and throughput separately, and pay for each.

Azure charges for size, IOPS and throughput on three separate meters A box, One Ultra Disk, holds three settings, with Microsoft's limits for one disk. Size, 4 GiB to 64 TiB. IOPS, up to 400,000. Throughput, up to 10,000 MB/s. Each setting has its own arrow, labelled per GiB set, per IOPS set and per MB/s set, to its own meter under the heading Charged by the hour. The three meters are the Capacity meter, IOPS meter and Throughput meter. Azure charges for size, IOPS and throughput on three separate meters One Ultra DiskCharged by the hourSize4 GiB to 64 TiBper GiB setCapacity meterIOPSup to 400,000per IOPS setIOPS meterThroughputup to 10,000 MB/sper MB/s setThroughput meter
Microsoft’s limits for one Ultra Disk: you set its size, IOPS and throughput separately, and each one is charged by the hour for what you set, not for the data or I/O you use.

Microsoft’s limits:

  • sizes from 4 GiB to 64 TiB, in 1 GiB steps
  • up to 1,000 IOPS per GiB, and 400,000 per disk
  • up to 0.25 MB/s for each IOPS you set, and 10,000 MB/s per disk

A database that needs speed more than space

Say a database holds 200 GiB but needs 150,000 IOPS. A 200 GiB Ultra Disk can reach 200,000 IOPS, if the VM’s limit allows it. One Premium SSD v2 stops at 80,000, and a Premium SSD at 20,000 base IOPS.

Azure Ultra Disk limitations

  • It works only as a data disk, never as the OS disk.
  • It’s locally redundant storage (LRS) only, with no zone-redundant storage (ZRS).
  • It doesn’t support availability sets or disk caching.
  • Only some regions and VM series support it.

Why it matters for your cloud cost

An Ultra Disk is charged by the hour for the size, IOPS and throughput you set, not for the data or I/O you use. Three things change what you pay:

  • You can change its performance up to four times in 24 hours, without detaching the disk. Each change can take up to an hour.
  • A VM with Ultra Disk compatibility on but no Ultra Disk attached pays a reservation fee per virtual CPU.
  • Azure’s one-year disk reservations don’t cover Ultra Disk.

The free assessment works out what your disks could save.

Read next: Premium SSD v2 vs Premium SSD: which one costs less?

Sources: Microsoft Learn, “Select a disk type for Azure IaaS VMs” (opens in a new tab); Microsoft Learn, “Understand Azure Disk Storage billing” (opens in a new tab); Microsoft Learn, “Configure Ultra Disks for Azure virtual machines” (opens in a new tab); Microsoft Azure, “Managed Disks pricing” (opens in a new tab).

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