Azure Premium SSD managed disks have two available bursting models: credit-based bursting and on-demand bursting. This article explains how to create a Premium SSD managed disk with on-demand bursting or enable on-demand bursting on an existing Premium SSD managed disk. 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.
For details on disk bursting, see managed disk bursting.
For the max burst targets on each supported disk, see Scalability and performance targets for VM disks.
Important
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 SSD managed disks. 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 you change the performance tier. If you want to change your performance tier but don't 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.
Enable on-demand bursting by deployment method
You can enable on-demand bursting with the Azure portal, Azure PowerShell, Azure CLI, or an Azure Resource Manager (ARM) template. The following examples show how to create a Premium SSD managed disk with on-demand bursting or enable on-demand bursting on an existing Premium SSD managed disk.
To enable on-demand bursting, an existing Premium SSD managed disk must be larger than 512 GiB and either detached from its VM or attached to a stopped VM.
To enable on-demand bursting for an existing disk:
- Sign in to the Azure portal and navigate to your disk.
- Select Configuration and select Enable on-demand bursting.
- Select Save.
On-demand bursting cmdlets are available in version 5.5.0 and newer of the Az PowerShell module.
Create an empty data disk with on-demand bursting
To enable on-demand bursting, a Premium SSD managed disk must be larger than 512 GiB. Replace the <myResourceGroupDisk> and <myDataDisk> parameters in the following script. The script uses Set-AzContext to select the subscription, New-AzDiskConfig to create a disk configuration, and New-AzDisk to create a Premium SSD managed disk with on-demand bursting:
Connect-AzAccount -Environment AzureChinaCloud
Set-AzContext -SubscriptionName <yourSubscriptionName>
$diskConfig = New-AzDiskConfig -Location 'chinanorth2' -CreateOption Empty -DiskSizeGB 1024 -SkuName Premium_LRS -BurstingEnabled $true
$dataDisk = New-AzDisk -ResourceGroupName <myResourceGroupDisk> -DiskName <myDataDisk> -Disk $diskConfig
Enable on-demand bursting on an existing disk
To enable on-demand bursting, an existing Premium SSD managed disk must be larger than 512 GiB and either detached from its VM or attached to a stopped VM. Replace the <myResourceGroupDisk> and <myDataDisk> parameters in the following command. The command uses New-AzDiskUpdateConfig to create an update configuration and passes it to Update-AzDisk to update the disk. To disable on-demand bursting, set -BurstingEnabled to $false.
New-AzDiskUpdateConfig -BurstingEnabled $true | Update-AzDisk -ResourceGroupName <myResourceGroupDisk> -DiskName <myDataDisk>
On-demand bursting commands are available in version 2.19.0 and newer of the Azure CLI.
Note
Before you can use Azure CLI in Microsoft Azure operated by 21Vianet, please run az cloud set -n AzureChinaCloud first to change the cloud environment. If you want to switch back to Azure Public Cloud, run az cloud set -n AzureCloud again.
Create and attach an on-demand bursting data disk
To enable on-demand bursting, a Premium SSD managed disk must be larger than 512 GiB. Replace the <yourDiskName>, <yourResourceGroup>, and <yourVMName> parameters in the following commands. Use az disk create to create a Premium SSD managed disk with on-demand bursting, and then use az vm disk attach to attach it to a VM:
az disk create -g <yourResourceGroup> -n <yourDiskName> --size-gb 1024 --sku Premium_LRS -l chinanorth2 --enable-bursting true
az vm disk attach --vm-name <yourVMName> --name <yourDiskName> --resource-group <yourResourceGroup>
Enable on-demand bursting on an existing disk
To enable on-demand bursting, an existing Premium SSD managed disk must be larger than 512 GiB and either detached from its VM or attached to a stopped VM. Replace the <yourResourceGroup> and <yourDiskName> parameters in the following az disk update command. To disable on-demand bursting, set --enable-bursting to false.
az disk update --name <yourDiskName> --resource-group <yourResourceGroup> --enable-bursting true
By using the 2020-09-30 disk API, you can enable on-demand bursting on newly created or existing Premium SSD managed disks larger than 512 GiB. The 2020-09-30 API introduced the burstingEnabled property, which is set to false by default. The following sample template creates a 1-TiB Premium SSD managed disk in China North 2 with on-demand bursting enabled:
{
"$schema": "http://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"diskName": {
"type": "string"
},
"diskSkuName": {
"type": "string",
"defaultValue": "Premium_LRS"
},
"dataDiskSizeInGb": {
"type": "int",
"defaultValue": 1024
},
"location": {
"type": "string",
"defaultValue": "chinanorth2"
},
"diskApiVersion": {
"type": "string",
"defaultValue": "2020-09-30"
}
},
"resources": [
{
"apiVersion": "[parameters('diskApiVersion')]",
"type": "Microsoft.Compute/disks",
"name": "[parameters('diskName')]",
"location": "[parameters('location')]",
"properties": {
"creationData": {
"createOption": "Empty"
},
"diskSizeGB": "[parameters('dataDiskSizeInGb')]",
"burstingEnabled": true
},
"sku": {
"name": "[parameters('diskSkuName')]"
}
}
]
}
Next steps
To learn how to gain insight into your bursting resources, see Disk bursting metrics.