Premium solid-state drives (SSD) have two available bursting models; credit-based bursting and on-demand bursting. This article covers how to switch to on-demand bursting. Disks that use the on-demand model can burst beyond their original provisioned targets. On-demand bursting occurs as often as needed by the workload, up to the maximum burst target. On-demand bursting incurs additional charges.
You don't need to follow the steps in this article to use credit-based bursting. By default, credit-based bursting is enabled on all eligible disks.
Before you enable on-demand bursting, understand the following:
On-demand bursting cannot be enabled on a premium SSD that has less than or equal to 512 GiB. Premium SSDs less than or equal to 512 GiB will always use credit-based bursting.
On-demand bursting is only supported on premium SSDs. If a premium SSD with on-demand bursting enabled is switched to another disk type, then disk bursting is disabled.
On-demand bursting doesn't automatically disable itself when the performance tier is changed. If you want to change your performance tier but do not want to keep disk bursting, you must disable it.
On-demand bursting can only be enabled when the disk is detached from a VM or when the VM is stopped. On-demand bursting can be disabled 12 hours after it has been enabled.
Currently, the on-demand model for disk bursting is available in all public Azure regions.
On-demand bursting can be enabled with either the Azure portal, the Azure PowerShell module, the Azure CLI, or Azure Resource Manager templates. The following examples cover how to create a new disk with on-demand bursting enabled and enabling on-demand bursting on existing disks.
Select Configuration and select Enable on-demand bursting.
On-demand bursting cmdlets are available in version 5.5.0 and newer of the Az module. Alternatively, you may use the Azure Cloud Shell.
Create an empty data disk with on-demand bursting
A managed disk must be larger than 512 GiB to enable on-demand bursting. Replace the <myResourceGroupDisk> and <myDataDisk> parameters then run the following script to create a premium SSD with on-demand bursting:
A managed disk must be larger than 512 GiB to enable on-demand bursting. Replace the <myResourceGroupDisk>, <myDataDisk> parameters and run this command to enable on-demand bursting on an existing disk:
New-AzDiskUpdateConfig -BurstingEnabled $true | Update-AzDisk -ResourceGroupName <myResourceGroupDisk> -DiskName <myDataDisk> //Set the flag to $false to disable on-demand bursting
A managed disk must be larger than 512 GiB to enable on-demand bursting. Replace the <yourDiskName>, <yourResourceGroup>, and <yourVMName> parameters, then run the following commands to create a premium SSD with on-demand bursting:
az disk create -g <yourResourceGroup> -n <yourDiskName> --size-gb 1024 --sku Premium_LRS -l westcentralus --enable-bursting true
az vm disk attach --vm-name <yourVMName> --name <yourDiskName> --resource-group <yourResourceGroup>
Enable on-demand bursting on an existing disk - CLI
A managed disk must be larger than 512 GiB to enable on-demand bursting. Replace the <myResourceGroupDisk> and <yourDiskName> parameters and run this command to enable on-demand bursting on an existing disk:
az disk update --name <yourDiskName> --resource-group <yourResourceGroup> --enable-bursting true //Set the flag to false to disable on-demand bursting
With the 2020-09-30 disk API, you can enable on-demand bursting on newly-created or existing premium SSDs larger than 512 GiB. The 2020-09-30 API introduced a new property, burstingEnabled. By default, this property is set to false. The following sample template creates a 1TiB premium SSD in West Central US, with disk bursting enabled:
"defaultValue": "Premium_LRS" //Supported on premium SSDs only
"defaultValue": "1024" //Supported on disk size > 512 GiB
"defaultValue": "westcentralus" //Preview regions: West Central US
"defaultValue": "2020-09-30" //Preview supported version: 2020-09-30 or above
"burstingEnabled": "true" //Feature flag to enable disk bursting on disks > 512 GiB