Azure: Find the number of Fault Domains for region

June 26, 2025 Leave a comment

A fault domain is a logical grouping of hardware within a data center that shares a common power source and network switch.

In cloud environments like Microsoft Azure or Oracle Cloud, fault domains help improve high availability by ensuring that resources (like virtual machines) are distributed across isolated hardware. This way, if a failure occurs in one fault domain (e.g., a power outage or hardware failure), it doesn’t affect the other domains.

In clustered environments such as Oracle RAC and others, it is highly recommended to distribute database nodes across different Availability Zones (preferably within close proximity). However, if the selected region does not support Availability Zones, or if the network latency between AZs is too high, you can instead distribute the nodes across different fault domains to ensure fault tolerance at the power and network switch level.

To verify how many fault domains are supported in your chosen region, run the following script from Azure CLI:

az vm list-skus --resource-type availabilitySets --query '[?name==`Aligned`].{Location:locationInfo[0].location, MaximumFaultDomainCount:capabilities[0].value}' -o Table

The output by June 11, 2025, is as follows (subject to change in the future):

Location            MaximumFaultDomainCount
------------------  -------------------------
AustraliaCentral    2
AustraliaCentral2   2
australiaeast       2
australiasoutheast  2
AustriaEast         2
BelgiumCentral      2
brazilsouth         3
BrazilSoutheast     2
CanadaCentral       3
CanadaEast          2
CentralIndia        3
centralus           3
CentralUSEUAP       1
ChileCentral        2
DenmarkEast         2
eastasia            2
eastus              3
eastus2             3
EastUS2EUAP         2
EastUSSTG           1
FranceCentral       3
FranceSouth         2
GermanyNorth        2
GermanyWestCentral  2
IndonesiaCentral    2
IsraelCentral       2
IsraelNorthwest     2
ItalyNorth          2
japaneast           3
japanwest           2
JioIndiaCentral     2
JioIndiaWest        2
KoreaCentral        2
KoreaSouth          2
MalaysiaSouth       2
MalaysiaWest        2
MexicoCentral       2
NewZealandNorth     2
northcentralus      3
northeurope         3
NorwayEast          2
NorwayWest          2
PolandCentral       2
QatarCentral        2
SouthAfricaNorth    2
SouthAfricaWest     2
southcentralus      3
SouthCentralUS2     2
SouthCentralUSSTG   2
southeastasia       2
SoutheastUS         2
SoutheastUS3        2
SoutheastUS5        2
SouthIndia          2
SouthwestUS         2
SpainCentral        2
SwedenCentral       3
SwedenSouth         2
SwitzerlandNorth    2
SwitzerlandWest     2
TaiwanNorth         2
TaiwanNorthwest     2
UAECentral          2
UAENorth            2
uksouth             2
ukwest              2
westcentralus       2
westeurope          3
WestIndia           2
westus              3
westus2             3
WestUS3             3

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Azure: Search for a specific VM series availability in region

February 11, 2025 Leave a comment

Use Azure CLI to retrieve available VM SKUs (sizes) in a specified region, filter them by a VM type, and formats the output.

In this specific case, I am checking whether the E20as_v6 and E20s_v6 sizes are available in the eastus2 region and determining the zones in which they are offered:

mari@Azure:~$ az vm list-skus --location eastus2 --all true --resource-type virtualMachines --output table | grep -E "E20as_v6|E20s_v6"

virtualMachines  eastus2      Standard_E20as_v6          1,2      None
virtualMachines  eastus2      Standard_E20s_v6           1,2      None

Explanation of command/options:

Command/OptionDescription
az vm list-skusLists available VM SKUs (sizes)
--location eastus2Specifies the Azure region (eastus2) where the VM SKUs should be retrieved.
--all trueShow all information including vm sizes not available under the current subscription.
--resource-type virtualMachinesFilters the SKU list specifically for virtual machines.
--output tableFormats the output into a readable table format instead of JSON.
| grep -E "E20as_v6|E20s_v6"Pipes (|) the output into grep, filtering only the lines containing E20as_v6 or E20s_v6.

Explanation of the result:

ValueDescription
NoneThis column usually shows restrictions, such as NotAvailableForSubscription. Here, “None” means no restrictions apply, and the VM SKU can be deployed without limitations.
1, 2VMs are available in 1 and 2 availability zones

E-Series VMs are optimized for memory-intensive workloads such as in-memory databases, and big data applications.

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