On regions, SKUs, quotas, and costs

This chapter is a bit different. It is not an end-to-end tutorial like the others, but a set of pointers and commands about regions, SKUs, quotas, and costs.

We have been provisioning VMs and specifying their SKUs. You may be wondering, where you can find which SKUs are available, what their properties are, how many can you get, how much they cost, etc.

DISCLAIMER: This document is work-in-progress and my personal experience performing this task.



Before we start, make sure you have azure cli installed and you are using the right subscription:

az account set -n <subscription name or id>

and to double check you are in the right subscription:

az account show

1. Regions

In Azure, data centers are spread in multiple physical geographies, like USA, Canda, Brazil, Africa, France, Japan, Australia, etc. Inside a geography you can find regions. For instance, in USA geography you can have EastUs, WestUS, South Central US, among other regions. In each region there are one to three availability zones, which are separated groups of datacenters in a particular region.

In this website you can find info about the geographies and regions:

https://azure.microsoft.com/en-us/explore/global-infrastructure/geographies

And here more info about availability zones:

https://learn.microsoft.com/en-us/azure/reliability/availability-zones-overview

To get the names of the regions using azure CLI:

az account list-locations -o table

Output will be something like:

DisplayName               Name                 RegionalDisplayName
------------------------  -------------------  -------------------------------------
East US                   eastus               (US) East US
East US 2                 eastus2              (US) East US 2
South Central US          southcentralus       (US) South Central US
...                       ...                  ...

2. SKUs

SKU, which stands for Stock Keeping Unit, is how a virtual machine size is called in Azure.

There are several SKUs in Azure to be selected for provisioning virtual machines.

2.1 SKU: Sizes

When selecting an SKU, one needs to understand the workload in which the virtual machine will host/process. There are different SKUs, to exemplify:

The following reference contains information about the SKU sizes:

https://learn.microsoft.com/en-us/azure/virtual-machines/sizes

Inside the link above, there are links to each group of SKU sizes, for instance:

The link below contains a VM selection advisor in which one can specify information about the target workload, and options about SKUs are presented:

If one wants to know the list of available SKUs, the following command can be used:

az vm list-skus --location eastus --output table
2.2 SKU: Naming

When selecting an SKU, one sees names such as Standard_E16d_v5, Standard_NC12s_v3, and Standard_HB176-48rs_v4. These names specify details about the SKU size.

The major blocks of these names are:

[Family] +
[Sub-family] +
[# of vCPUs] +
[Constrained vCPUs] +
[Additive Features] +
[Accelerator Type] +
[Version]`

Additive Features:
a = AMD-based processor
b = Block Storage performance
d = diskful (that is, a local temp disk is present); this feature is for newer Azure VMs, see Ddv4 and Ddsv4-series
i = isolated size
l = low memory; a lower amount of memory than the memory intensive size
m = memory intensive; the most amount of memory in a particular size
p = ARM Cpu
t = tiny memory; the smallest amount of memory in a particular size
r = remote direct memory access (RDMA) connectivity
s = Premium Storage capable, including possible use of Ultra SSD (Note: some newer sizes without the attribute of s can still support Premium Storage, such as M128, M64, etc.)
C = Confidential
NP = node packing
Full description of the naming conventions can be found here:

https://learn.microsoft.com/en-us/azure/virtual-machines/vm-naming-conventions

Here is the link to describe about constrained vCPUs, which are VMs that have a reduced number of cores but maintaining their original properties such as memory size. One of the use cases for such constrained vCPUs is to save software licensing costs, as some licenses are based on the number of cores a VM has.

https://learn.microsoft.com/en-us/azure/virtual-machines/constrained-vcpu

3. Quotas

Each subscription has an associated quota, which defines how many machines / cores of a given SKU can be rented per region.

To get the quota and its usage for all SKUs of a given region:

az vm list-usage --location <region> --out table
az vm list-usage --location eastus --out table

To get the usage and quota for a specific region and specific SKU

az vm list-usage --location <region> | grep <sku>
az vm list-usage --location centralus -o table  | grep "Standard HBv4"
az vm list-usage -l eastus -o table | grep "Name\b\|---\|HB\|NV\|NC"

You can use az quota command to manage (e.g. request new quota). See details in the following url:

https://learn.microsoft.com/en-us/cli/azure/quota?view=azure-cli-latest

4. Costs

Details on costs can be found here:

https://azure.microsoft.com/en-us/pricing/details/virtual-machines/linux/

There is also this site below which is not the official azure site but can be helpful:

https://azureprice.net/

For costs, you can leverage the rest api from Microsoft Azure. Details of the api can be found here:

https://learn.microsoft.com/en-us/rest/api/cost-management/retail-prices/azure-retail-prices

In this website above, there is a code available in python to use the rest api, with some hard coded values.

In this git folder, there is a slightly modified version of the code to obtain the cost using the region and sku as arguments:

python3 get_price.py  westus3 Standard_HB120rs_v3
python3 get_price.py  canadacentral Standard_HC44rs

There is also another modified version you can look for price for linux machine without being Low Priority or Spot and you can look for the sku name ignoreing the case:

The get_price.py script has a few lines of code and can be easily modified to explore more filters of the rest api.

python3 get_price_linux.py    westus3 standard_HB120rs_v3

References