Azure Shared Disks in Preview!

Introduction

Microsoft’s newest disk offering answers our cries for being able to use a single disk across multiple VM’s. The first use I can consider would be for clustering and use of a witness disk. You can read more about clustering here: Windows Server Failover Cluster (WSFC).

Summary

Currently this feature requires filling out a request form: https://microsoft.qualtrics.com/jfe/form/SV_3Dh5KrErF9itiUR

There are certain limitations and specific setup after being accepted into the preview. Let’s talk about a few of the limitations first (provided by Microsoft).

Currently only available with premium SSDs.
Currently only supported in the West Central US region.
All virtual machines sharing a disk must be deployed in the same proximity placement groups.
Can only be enabled on data disks, not OS disks.
Only basic disks can be used with some versions of Windows Server Failover Cluster, for details see Failover clustering hardware requirements and storage options.
ReadOnly host caching is not available for premium SSDs with maxShares>1.
Availability sets and virtual machine scale sets can only be used with FaultDomainCount set to 1.
Azure Backup and Azure Site Recovery support is not yet available.

Additionally, your disk must be created with the value maxShares>1. Your Virtual Machine also must reside in a Proximity Placement Group. This forces the machines to remain as close as possible to reduce latency.

Here’s a sample via PowerShell on how to create a placement group

$resourceGroup = "myPPGResourceGroup"
$location = "East US"
$ppgName = "myPPG"
New-AzResourceGroup -Name $resourceGroup -Location $location
$ppg = New-AzProximityPlacementGroup 
   -Location $location
   -Name $ppgName 
   -ResourceGroupName $resourceGroup
   -ProximityPlacementGroupType Standard