Many businesses who are planning to migrate to Azure, see Azure SQL Database Managed Instance as a simple way to make the transition and there is good reason for this. It’s a great product with a lot of positive features. However, at this point in time, Azure Managed Instance has some key limitations that could mean it is not an option for your project. Forewarned, as they say, is forearmed. Read on to learn about the four key limitations to consider when assessing Azure Managed Instance as your pathway to the cloud.
The benefits of Azure Managed Instance
There are certain types of business and migration scenarios for which Azure Managed Instance is a strong choice. In general, this is typically larger companies who want to accelerate their journey to Azure, but who are not yet prepared for the extensive re-engineering that comes with the reduced feature set of the “Platform-as-a-Service (PaaS)” solution provided by Azure SQL Database or Elastic Pools.
In this case, Azure Managed Instance is often a good ‘middle ground’. It provides the control of an Infrastructure-as-a-Service (IaaS) environment and the benefits of a PaaS environment at a similar cost to an on-premises SQL Server environment.
To put it plainly, Azure Managed Instance is a simple and fast way to migrate if you meet all the criteria.
At WARDY IT Solutions, we’ve identified a few ‘fine print’ details not all businesses are aware of, which should be taken into consideration.
Microsoft has done a great job of resolving some of the issues associated with Azure Managed Instance and the functionality is improving all the time. No doubt they will continue to improve this product over time.
For now though, it is worthwhile examining the existing limitations to ensure your business requirements will be met by the platform and your existing systems meet the criteria.
- Lack of application vendor support
There is currently little application vendor support for this product. If your current SQL Server supports an application that does not support Azure Managed Instance, you may not have access to vendor support, which could be a critical drawback.
For example, even SharePoint applications are currently not supported by Microsoft when running on the Azure Managed Instance platform. The same is true for Azure SQL Database.
None of the big application vendors have thus far announced support for Azure Managed Instance but this will most likely come with time.
- Windows authentication not supported
For on-premise and IaaS servers, there are two authentication methods: Windows authentication and SQL authentication. We find most of our clients use Windows authentication because it is the most secure option.
The catch with Azure Managed Instance is that it doesn’t currently support Windows authentication. This isn’t necessarily a showstopper, as you can use SQL authentication or migrate to the new Azure Active Directory Authentication, but it is worth checking with your application vendor or internal application development team.
Be warned, Azure Managed Instance will be completely unusable if your application relies on Windows authentication.
Relying on SQL authentication only could lead to security issues. You can’t lock accounts as quickly with this authentication method. You will need to log on to every server and lock each app individually which is both a logistical, and a time-consuming nightmare.
- Some key database restrictions
There are limits to both the number and the size of the databases when it comes to using Azure Managed Instance.
The maximum number of databases is 100. If you have 130 databases, you will need to build two Managed Instance servers – effectively doubling your costs. This is not to mention that running two environments instead of one is an administrative challenge.
When it comes to the size of the databases, Managed Instance offers two tiers:
- Tier 1: General purpose (8 TB) which is fine for most companies
- Tier 2: Business-critical (1-4 TB) which offers higher performance, but with less total storage and higher costs.
For business-critical tier Managed Instances, the maximum database size depends on the number of cores on the server. Managed Instances are charged based on the number of cores you will need. This is charged in blocks of storage:
- 8-16 cores: 1 TB
- 24 cores: 2 TB
- 32 cores or above: 4 TB
Many businesses would have more than 1 TB on a server. This would mean moving up to 24 cores (in order to get 2 TB) which could mean having far more cores than you need and thereby wasting money on CPU resources that are not beneficial to your organisation.
For example, a company we have worked with recently only required 8 cores to support 3 TB of databases. To migrate to Azure Managed Instance, they would have had to purchase 3 times the number of cores required to ensure enough storage for the databases.
- Minimum core purchase
Related to the above point is that the minimum number of cores you can purchase is eight. Many companies only need four core servers, so they end up paying for twice as much as what they need.
Managed Instance is an excellent choice for certain businesses and situations. With this limitation, Azure Managed Instance is usually a better fit for workloads running on existing servers with larger core counts, rather than smaller servers below 8 cores.
Ask the right questions and seek good advice
Azure Managed Instance is a great solution. As a ‘lift and shift’, it provides the perfect way for many businesses to migrate from fully self-managed systems, on-premise or IaaS to a cloud-based PaaS solution.
If you are considering Azure Managed Instance, we suggest you do your due diligence or seek expert advice.
At WARDY IT Solutions we are experts in Azure migrations and can quickly identify whether Managed Instance is the right solution for your business and if not, what other options are more suited to your requirements.
If migrating to the cloud is on your agenda, please feel free to get in touch, or schedule a complimentary half-day workshop with our Azure specialists to find out if Azure Managed Instance is a good fit for you.Contact us
2 thoughts on “Four catches to watch out for when considering Azure Managed Instance”
No mention of T-SQL features in the article, is Azure SQL also a cut-down version of SQL Server Enterprise?
This following article outlines the differences in syntax and behaviour between Azure SQL Database Managed Instance and on-premises SQL Server Database Engine – https://docs.microsoft.com/en-us/azure/sql-database/sql-database-managed-instance-transact-sql-information
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