AZ-104 Certification Notes

Chapter 9.3 - Managing Virtual Machine Disks

What Are Virtual Hard Disks?

• Virtual Hard Disks (VHDs)
  • A file representation of what is found on a hard disk
  • Virtual machines (VMs) use VHDs to store OS, apps, and data. VHDs utilize the underlying Microsoft storage infrastructure. They are stored as page blobs in the blob services

Purpose of VHDs

• OS Disk
  • Default with virtual machines
  • Stores the operating system
  • Registered as a SATA drive
  • Labeled as the C: drive for Windows and mounted at "/" for Unix-like systems
  • Max capacity of 4,095 GiB
• Temporary Disk
  • Default with virtual machines
  • Stores non-persistent data like page and swap files
  • Local disk for the underlying Microsoft Infrastructure
• Data Disk
  • Additional disks attached to a VM
  • Used for storing persistent data like files or databases
  • Registered as a SCSI drive
  • Max capacity of 32,767 GiB

Unmanaged vs. Managed Disks

• Unmanaged
  • Not an Azure Resource Manager (ARM)-managed resources
  • Manually managed storage accounts
  • Availability not guaranteed
• Managed
  • An Azure Resource Manager (ARM)-managed resource
  • Azure-managed storage accounts
  • Availability Supported
  • Role-Based Access Control (RBAC)
  • Snapshot Support
  • Backup Support

Major Disk Types

• Disk Type:
  • Ultra Disk (SSD)
    • I/O-intensive workloads like top tier Online Transactional Processing (OLTP), any transaction-heavy workloads. (Only used as a data disk)
  • Premium (SSD)
    • Production and performance workloads
  • Standard (SSD)
    • Web servers, light enterprise applications, and dev/test workloads
  • Standard (HDD)
    • Backup, non-critical workloads

Disk Encryption at Rest for Defense in Depth

• Storage Service Encryption (SSE)
  • Encryption of physical disks in the data center
  • Built into Azure platform
• Azure Disk Encryption (ADE)
  • Optional encryption of the VHDs
  • Ensures a disk is only accessible by the VM that owns the disk
  • OS tools like BitLocker and DM-Crypt

Demonstration

• Add a Data Disk to a VM
  • Use Azure Portal in Cloud Playground to add a data disk
• Enable Azure Disk Encryption
  • Create a key vault, create a key, and select encryption settings
• Validate Encryption
  • Use PowerShell to validate encryption

Exam Tips

• Azure Disks = VHD
  • OS Disk
  • Temporary Disk
  • Data Disk