Q. Are there any special considerations when creating clusters in Azure IaaS?
A. Azure IaaS enables the creation of VMs on the Azure fabric however there are some key considerations that impact architecture based on the capabilities of the Azure platform.
- There is no native shared storage in Azure IaaS however there are ways to enable the availability of shared storage either via an iSCSI service running in an IaaS VM or using Storage Spaces Direct (S2D) in Windows Server 2016 that enables local storage to each host to be abstracted and joined to present a cluster shared volume. There is also Azure Files which is an SMB 3.0 file server (but has limited ACL capabilities)
- Because of the lack of shared storage and lack of ACLs on Azure Files, for 2016 clusters you should use Cloud Witness (a storage account selected in Azure) for the quorum and pre-2016 one option is to create a file server VM and create a share which can be the file share witness for the cluster
- By default NICs have only a single IP address and normally the cluster has an additional IP address and then certain cluster roles have additional IP addresses. This may require the use of load balancers or other configurations to correctly handle the IP address requirements. Note that with the addition of multiple IP configurations per NIC capability and multiple load balancers the exact IP address solutions for clusters in Azure will be evolving