Azure shared disks – Failover Clustered Instances

Azure offers a large array of options when it comes to high availability and disaster recovery. Failover clustered instances (FCIs) is a well known option, for SQL Server, that’s been available for years on premises. However, FCIs traditionally required shared storage. New versions of the Windows OS and SQL Server now support other options such as file shares and storage spaces direct. Each of these options have their pros and cons. As of July 27th, 2020 Azure Shared Disks are generally available. We’ll focus on this option for both SQL Server 2016 and SQL Server 2019 over the next couple blog posts.

Why should I care about shared disks?

Azure shared disk enable the ability to utilize FCIs and reduce storage consumption. Previously, if you created an FCI instance and didn’t want to use a file share, storage spaces direct was required and doubled the amount of space needed. Another option was to set up Availability Groups. Again, doubling the space and possibly requiring Enterprise editions of SQL Server (prior to basic availability groups being introduced). If you’re needing to migrate to Azure, and utilize IaaS vs PaaS and retain high availability, this is a great addition to the array of available options. Plus, unless you specifically need Enterprise edition features, you may be able to keep Standard edition further reducing costs.

What type of disks do I need to use?

Shared disks are currently available on two disk types; ultra and premium. Each type has there own list of limitations. Rather than listing those here, and the information becoming out of date, review the following links for the most up to date information;

1. Using Azure Ultra Disks
2. Premium SSDs

Which regions are shared disks currently available in?

Shared ultra disks are available within all regions which currently support ultra disks. See here for the latest list of regions. Premium shared disks are available in the regions listed here. If you’re using premium shared disks, you’ll need to request access using the form located at https://microsoft.qualtrics.com/jfe/form/SV_cMCj3LBlv47M6xL.

How do I get started?

This is an exciting option for those looking to migrate on-premises failover clustered instances to Azure with little modification. To get started, review Microsoft’s latest announcement, and the links provided above, to determine if this is the right option. We’ll be creating additional posts over the next few weeks detailing how to setup two node clusters using Windows Server 2019, SQL Server 2016, and SQL Server 2019. There are some major differences when using SQL Server 2016 and SQL Server 2019 which will be explained throughout the posts. SQL Server 2016 FCIs requires the use of an Azure load balancer and we’ll provide examples of a complete setup. SQL Server 2019 CU2 introduces a new feature, distributed network name, which further simplifies setup. You can read more on this feature here.

How can we help?

We’d be more than happy to discuss your move to Azure FCIs or any upcoming migration projects. Contact us here to schedule a call.

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