DevOps Peach

Azure Basics · Virtual Machines – Sizes, Disks, Connecting, Availability and Scale Sets · Lesson 1 of 5

Planning a VM — Network, Name, Region, Pricing and Size

Before creating a VM decide its network, name, region, pricing model and size; the series letter tells whether a VM is optimised for CPU, RAM, disk or GPU.

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A VM is IaaS: you manage the OS, patches and software; Azure manages the hardware. Uses: dev/test, websites, backup/DR, HPC, big data, extending a datacenter.

Checklist

  1. Network first: VNet, subnet, NSG (moving a VM to another VNet later is hard).
  2. Name: follow a convention (for example vm-web-01).
  3. Region: close to users, offering the sizes/services you need, within data rules; prices differ between regions.
  4. Pricing: compute (per second while running) + storage (disks are billed even when the VM is stopped). Models: pay-as-you-go, 1–3 year Reservations, Spot (cheap, can be evicted), Azure Hybrid Benefit.
  5. Size: by vCPUs, RAM, disks, network.
Series Optimised for
B Burstable, low load with occasional spikes — cheap
D General purpose
E, M Memory optimised (M: very large RAM)
F Compute optimised (high CPU)
L Storage optimised
N GPU
H HPC 
flowchart LR
  N["1. Network"] --> T["2. Name"] --> R["3. Region"] --> G["4. Pricing"] --> S["5. Size (series)"]

Traps: F is compute, M is memory; N means GPU, not "network". Old series such as A and G are retired or retiring. Change size (scale up/down) with az vm resize; if the new size is not available on the current cluster, deallocate first.

Command Meaning
az vm list-skus -l southeastasia --size Standard_B -o table B-family sizes in the region (list-sizes is deprecated)
az vm resize -g rg-devops-lab -n vm-web --size Standard_B2s Change the size

Reading a size name

Standard_D4ads_v5 can be decoded piece by piece:

Part Meaning
D Family (general purpose)
4 Number of vCPUs
a AMD processor (p means Arm-based)
d Has a local temporary disk
s Supports Premium SSD
v5 Generation of the series

Other letters include l (lower memory per vCPU) and m (more memory). Newer generations are usually faster and cheaper for the same vCPU count.

Burstable B-series

B-series VMs earn CPU credits while running below a baseline and spend them when the load spikes. A VM that runs hot all the time drains its credits and is throttled to the baseline, so B-series suits small web servers and dev boxes, not steady batch work.

Checking availability and quota

Not every size exists in every region or zone. az vm list-skus -l southeastasia --zone --resource-type virtualMachines -o table shows sizes and their zones, and any restrictions for your subscription. vCPU quotas apply per region and per family, so a new deployment can fail even when the size exists; request an increase before a big rollout.

Getting the size right

Start from measured needs (CPU, memory, disk IOPS, network) rather than guessing high. After a few weeks, Azure Advisor flags underused VMs that can be resized or shut down. Arm-based sizes (for example Cobalt or Ampere processors) often give better price-performance for Linux workloads that run on Arm.

Special options

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