AZ-104 Certification Notes

Chapter 10.7 - Azure Disks CheatSheet

Azure Disks CheatSheet

Azure Managed Disks are block-level storage volumes that are managed by Azure and used with Azure VMs
Managed disks are designed for 99.999% availability
Azure creates three replicas of your data, allowing for high durability
You can create up to 50,000 VM disks of a type in a subscription per region
Allowing you to create up to 1,000 VMs in a virtual machine scale set using a Marketplace image
Managed disks are integrated with availability sets
Managed disks support Availability Zones
Azure Backup can be used to create a backup job with time-based backups and backup retention policies
You can use Azure role-based access control (RBAC) to assign specific permissions for a managed disk to one or more users
You can directly import your Virtual Hard Drive Disks (VHD) into Azure Disks
You can use Azure Private Links to ensure traffic between Azure Disks and VMs stay within the Microsoft network
Azure Managed Disks supports 2 types of encryption:
- Server Side Encryption (SSE) enabled by default for all managed disks, snapshots, and images
  - Temporary disk are not encrypted by server-side encryption unless you enable encryption at host
  - Keys can be managed two ways:
    - Platform-managed keys - Azure manages your keys
    - Customer-managed keys - You manage your keys
- Azure Disk Encryption (ADE) allows you to encrypt the OS and Data disks used by an IaaS Virtual Machine
- For Windows encryption is done by BitLocker
- For Linux encryption is done by DM-Crypt
There are 3 main disk roles in Azure, the data disk, the OS disk, the temporary disk
Data Disk
- A managed disk that's attached to a virtual machine to store application data, or other data you need to keep
- Registered as SCSI drives and are labeled with a letter that you choose
- Has a maximum capacity of 32,767 gibibytes (GiB)
- The size of the VM determines how many data disks you can attach and the type of storage you can use
OS Disk
- Every virtual machine has one attached operating system disk
- That OS disk has a pre-installed OS, which was selected when the VM was created
- This disk contains the boot volume
- This disk has a maximum capacity of 4,095 GiB
Temporary Disk
- Most VMs contain a temporary disk, which is not a managed disk
- Provides short-term storage for applications and processes, and is intended to only store data such as page or swap files
- Data on the temporary disk may be lost during a maintenance event or when you redeploy a VM
- During a successful standard reboot of the VM, data on the temporary disk will persist
- The temporary disk is typically /dev/sdb and on Linux and Windows VMs the temporary disk is D: by default
- Not encrypted by SSE unless you enable encryption at host
A managed disk snapshot is a read-only crash-consistent full copy of a managed disk that is stored as a standard managed disk by default
- Snapshots are point in time recovery
- Snapshots exist independent of the source disk and can be used to create new managed disks
- Snapshots are billed based on the used size (if you have a 64 GB drive and only use 10 GB you're only billed the 10 GB)
- You can see the used size of your snapshots by looking at the Azure Usage Report
A managed custom image create an image (of your disk from your VM. Contains all managed disks associated with a VM, OS and data disks)
A snapshot doesn't have awareness of any disk except the one it contains
For a single disk use a managed disk snapshot, for multiple disks such as striping use a managed custom disk
Azure offers 4 tiers of disks: Ultra Disks, Premium SSD, Standard SSD, Standard HDD

Ultra Disks deliver high throughput, high IOPS, and consistent low latency disk storage for Azure VMs
- Dynamically change the performance of the disk, without the need to restart your VM
- Suited for data-intensive workloads such as SAP HANA, top tier databases, and transaction-heavy workloads
- Can only be used as data disks (use a Premium SSD for OS Disk), only supported with very specific VM series
Premium SSD high-performance and low-latency disk supports for Azure VMs with input/output (IO)-intensive workloads
- Suitable for mission-critical production applications
- Only be used with VM series that are premium storage-compatible
- Guaranteed IOPS, and throughput of that disk (Standard tiers don't have IOPS guarantees)
- Designed to provide low single-digit ms latencies and target IOPS and throughput described in the preceding table 99.9% of the time
Standard SSD cost-effective storage option optimized for workloads that need consistent performance at lower IOPS levels
- Compare to standard HDDs, standard SSDs deliver better availability, consistency, reliability, and latency
- Suitable for Web Servers, low IOPS application servers, lightly used enterprise applications, and Dev/Test workloads
- Designed to provide single-digit ms latencies and the IOPS and throughput up to the limits described in the preceding table 99% of the time
- IOPs and throughput may vary sometimes depending on the traffic patterns, available on all Azure VMs
Standard HDD reliable, low-cost disk support for VMs running latency-insensitive workloads
- Available on all Azure VMs
- Latency, IOPS, and throughput of Standard HDD disks may vary more widely as compared to SSD-based disks
- Designed to delivery write latencies under 10 ms and read latencies under 20 ms for most IO operations
- Available in all Azure regions and can be used with all Azure VMs

Practice Quiz

Which type of disk role provides short-term storage for applications and processes, and is intended to only store data such as page or swap files?
- Permanent Disk
- Temporary Disk
- OS Disk
- Data Disk
What disk type is a cost-effective storage option optimized for workloads that need consistent performance at lower IOPS levels?
- Standard SSD

Chapter 10.6 - Bursting Chapter 11 - Introduction to Application Gateway