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Azure Managed Disks

Updated Nov 16, 2020 ·
NOTES

This is not an exhaustive documentation of all the existing Azure Services. These are summarized notes for the Azure Certifications.

To see the complete documentation, please go to: Azure documentation

Overview​

Azure virtual machines (VMs) use Azure disks as their attached disk storage.

  • Azure disks are built-on top of page blobs which are the type of blobs optimized for random access.
  • When you create Azure disks you can choose to manage the storage account yourself or to use managed disks where Azure manages the storage account for you.
  • Managed disks are the preferred option.

Azure Managed Disks provide a virtualized, scalable, and highly available storage solution for Azure VMs.

  • Virtualized block-level storage volumes used with Azure VMs and managed by Microsoft Azure.

  • The encryption options (SSE and ADE) enhance data security, and the distinction between data, OS, and temporary disks allows for efficient and purpose-driven disk management within the Azure infrastructure.

Benefits​

  1. Availability
    • Designed for 99.999% availability with three replicas of data per disk, protecting against two failures of disk replicas.
  2. Scalability
    • Supports up to 50,000 VM disks of a specific type per region in each subscription, enabling the creation of numerous virtual machines.
  3. Integration
    • With availability sets:
      • Isolation of VM disks within an availability set, guarding against a single point of failure within an Azure data center.
    • With availability zones:
      • Protection against entire Azure data center failures.
  4. Backup and Restore
    • Integrated with Azure backup, supporting backup and restore of managed disks, making VM restores easy.
  5. Access Control
    • Granular access control through Azure role-based access control (RBAC), allowing specific permissions for managed disks.
  6. Upload Ease
    • Facilitates the upload of on-prem VMs to Azure through direct upload, streamlining the VHD file transfer process.

Encryptions​

  1. Server-side Encryption (SSE)
    • Default for all managed disks.
    • Provides encryption at rest for data, snapshots, and images.
  2. Azure Disk Encryption (ADE)
    • Enables encryption on OS and data disks of a VM.
    • Uses BitLocker for Windows VMs
    • Used DM-crypt for Linux VMs.

Disk Types​

  1. Data Disks

    • Attached to a VM to store applications and data.
    • Registered as a SCSI drive, assignable drive letters,
    • Max capacity of 32 terabytes.
    • Number of data disks depends on VM size.

  2. OS Disks

    • Deployed with a VM, hosts OS and boot volume.
    • Max capacity of 4 terabytes.

  3. Temporary Disks

    • Not a managed disk, not intended for important data.

    • Every VM contains a temporary disk,

    • Used for page files and swap files,

    • Data may be lost during maintenance events or VM redeployment.

    • Assigned the drive letter D on Windows and

    • Assigned to /dev/sdb on Azure Linux VMs.