Attaching an array of data disks to a VM

[snarkbe]

Hi,

I create a bunch of data disks using an array of sizes given as parameter, along with the VM name:

param vmName string
param location string = resourceGroup().location
param datasizes array 

resource datadisk 'Microsoft.Compute/disks@2021-04-01' = [for (datasize, lun) in datasizes: {
  name: '${vmName}-DATA00${lun}'
  location: location
  sku: {
    name: 'StandardSSD_LRS'
  }
  properties: {
    creationData: {
      createOption: 'Empty'

    }
  diskSizeGB: datasize
  osType: 'Windows'

  }
}]

output datadisksId array = [for i in range(0, length(datasizes)): {
  name: '${vmName}-DATA00${i}'
  id: datadisk[i].id
}]

As output, I get an array of disk IDs. But I could get any other parameters from the disk resource.

However how can I attach these disks to the VM that is created in another module, using the output of this module?
I tried several ways to declare them in the Microsoft.Compute/virtualMachines resource, under properties/storageProfile/dataDisks.

Thanks!

[brwilkinson]

Do you really need to create the disks ahead of time, then use the attach option?

This is not common.

Most often the vm or Vmss allows you to create the disks directly as part on the VM definition.

Docs here:

https://docs.microsoft.com/en-us/azure/templates/microsoft.compute/virtualmachines?tabs=bicep#datadisk

[brwilkinson]

Nice one, that is the recommended way since the disks have the create option of empty instead of attach.

That setting can never be modified.

You could do something similar if you did need to create some DATA managed disks, outside of the initial deployment as well, using a similar format.

[frontegi]

I used the same syntax for some VMs, working fine. Now I'm trying to set a Managed Disk flag ( on-demand bursting -> burstingEnabled=true) during the VM creation.
This flag is not available there, while it is available if you create Disks outside of the initial deployment.
I'd like to understand if this can be achieved in any elegant way.

[brwilkinson]

@frontegi does it give you an error when you add burstingEnabled: true on the disk during vm creation ?

Do you happen to have the error? Also I assume you are using a later api version?

[brwilkinson]

adding link to docs for others interested to review the setting.
https://docs.microsoft.com/en-us/azure/virtual-machines/disks-enable-bursting?tabs=azure-resource-manager#get-started

[JustinGrote]

@brwilkinson I ran into this for a very clear use case: Shared Disks. If you want to do shared disks, you have to create them first as top level resources and then associate them to multiple VMs. This works fine if I just define them as is, but if I want to keep things DRY and use a loop, sadly I have to use an integer loop and can't do foreach.

Truncated Example:

resource sharedDisk 'Microsoft.Compute/disks@2022-03-02' = [for i in range(0, 9): {
  location: location
  name: '${vmName}-data${i}'

  properties: {
    creationData: {
      createOption: 'Empty'
    }
    diskSizeGB: 1023
    maxShares: 2
    tier: 'P30'
    osType: 'Windows'
  }
}]

resource vm 'Microsoft.Compute/virtualMachines@2021-03-01' = {
  name: vmName
  location: location
  properties: {
    dataDisks: [for i in range(0,9): {
      lun: i
      createOption: 'Attach'
      managedDisk: {
        id: sharedDisk[i].id
      }
    }]
  }
}