VM sizes and families
What it is
A VM size is a standard combination of vCPUs, memory, temporary storage, and network bandwidth offered by Azure (e.g. Standard_D2s_v3). Sizes are grouped into families (series) optimized for different workloads — General purpose (D), Compute optimized (F), Memory optimized (E), Storage optimized (L), GPU (N), High performance compute (H), Burstable (B).
Why it exists
Compute demand varies wildly. Size families let you right-size — pay only for the CPU/memory profile your workload actually needs, and scale up (change size) or out (scale sets) as demand changes.
Key ideas
- Name anatomy:
<Family>-<vCPU>-<series>-<generation>e.g.D2s v3= D-family, 2 vCPUs, Standard, v3 generation. - B-series (burstable): baseline credit accrual, bursts on demand — cheap for dev/test and low-steady-load workloads.
- Ephemeral vs managed storage couples with disk choices and the temporary disk (D:/tmp on Windows).
The three pieces (memorize!)
- vCPU count → compute capacity.
- Memory (GiB) → concurrent workloads / in-memory data.
- Temporary disk size + max network bandwidth → local scratch space and possible throughput.
How it fits (diagram)
Exam notes
- Resizing a VM requires deallocating it first (the new size may not fit the current host).
- vCPU quotas are per-family and per-region — you may need a quota-increase request before provisioning many VMs.
- The temporary disk is NOT persisted; a resize/restart can wipe it. Put persistent data on data disks.
- Introducing a size too small for the workload → poor performance, not an error; resize up with deallocate → resize → start.
- AZ-104 care about choosing an appropriate size and knowing family purpose, not memorizing every SKU.
Related
Path MOC · azure-vm · virtual-machine-scale-set · managed-disks
📘 Source: Microsoft Learn — Vm Sizes