Azure Learning

managed-disks

Properties2
tagscompute, storage, azure-vm, disks
aliasesManaged disk, Managed Disks, disk storage

2 min read

Azure managed disks

What it is

A managed disk is a block-level storage volume Azure creates and manages for you behind a VM — the OS disk and data disks. Microsoft handles the underlying storage accounts; you specify disk type, size, and redundancy. Unmanaged disks (storage-account backed, VM-scoped 20k IOPS cap) are legacy.

Why it exists

Disk management was a pain: unmanaged disks tied performance to a storage account and had an IOPS ceiling. Managed disks hide that — you pick a UI/SSD/HHD tier and Azure places it for scale and high availability automatically.

Key ideas

  • Disk types: Premium SSD (low latency, production), Standard SSD (consistent, entry production), Standard HDD (backup, sparse access), Ultra disk (extreme IOPS for data-heavy), plus Premium SSD v2.
  • Ephemeral OS disk: OS disk stored on the VM’s local temporary storage — resets on deallocate/restart but gives lower latency and lower cost; ideal for stateless or scale-out workloads (e.g. scale sets) and the cache/batch tier.
  • OS disk vs data disks: one OS disk, up to many data disks; each has a size and type.
  • Snapshots & images: snapshots capture a point-in-time copy; images are generalized system images reused for provisioning.
  • Redundancy: zone-redundant and locally-redundant disk options.

How it fits (diagram)

managed-disks - Microsoft diagram

Diagrams courtesy of Microsoft Learn / Azure docs: virtual-machines/managed-disks-overview

Exam notes

  • Max 4 TiB typical per-managed-disk scalability is governed by size tier; data disk IOPS/throughput scale with disk size (choose size = choose guaranteed IOPS).
  • Ephemeral OS disk: benefits = free, low latency; trade-off = data lost on deallocate/restart and VM size must support it. Only for cache/temp workloads.
  • Detach a data disk to move it to another VM (persistent disks survive VM deletion unless otherwise deleted).
  • OS/data disk encryption uses Azure Disk Encryption or server-side encryption; SSO/managed-identity prep not required for the exam details.
  • Snapshots → new disks or images is the standard backup/migration path. az vm disk snapshot / portal Snapshot button.

Path MOC · azure-vm · vm-snapshot · availability-set · virtual-machine-scale-set

📘 Source: Microsoft Learn — Managed Disks

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