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Azure VMware Solution is a hyperconverged vSphere cluster that leverages an all-flash VMware vSAN software-defined storage system. vSAN is a powerful software-defined storage system, offering many great features available when using Azure VMware Solution.
Like with any storage solution, there are ways to optimize the consumption of the disk. VMware vSAN enables tuning of each VMs storage policy. The granularity goes much deeper than just the VM; each disk attached to the VM can have its own storage policy.
This default storage policy applied to any disk created in the Azure VMware Solution private cloud is 1 failure – RAID-1 (Mirroring). In other words, one host can fail, and no data will be lost. Twice the amount of raw disk is needed to support the consumed disk in this configuration. When a vSAN cluster is only three nodes, this is the only policy available. See this blog article to understand how to modify Azure VMware Solution disk storage policies as the cluster grows.
The typical lifecycle of an Azure VMware Solution private cloud is the initial three (3) node deployment; then, the migration of virtual machines begins from on-premises to Azure VMware Solution, or workloads grow organically. Of course, as more and more VMs begin to fill the three-node cluster, at some point, the cluster nodes need to be expanded to a 4th, 5th, 6th, etc. This ability to grow and shrink the cluster on demand is the beauty of cloud-scale, and more explicitly, running VMware in the cloud. On-premises VMware clusters so many times are overprovisioned, which presents a whole new set of challenges. No need to do that with Azure VMware Solution.
As the cluster grows, more storage policies are available. Here is a complete list of storage policies that are available for Azure VMware Solution VM disks.
If the storage policy used on the virtual machine disks continues to be the same, as the cluster grows, the vSAN cluster will quickly fill. RAID 5/6 policies give a much more efficient use of storage vs. the RAID 1 configuration.
As the Azure VMware Solution private cloud grows beyond three nodes, choose which type of storage policy is best for the VM disks. Then go back and reconfigure the storage policies on the disks of the VMs deployed when the cluster was a three-node cluster.
By doing this, you are optimizing the storage consumption of the Azure VMware Solution cluster, maximizing the investment.
The table below is from the VMware vSAN Design Guide. As you can see, it outlines the types of RAID configurations available and the number of hosts required based on the failures to tolerate needed.
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