Why You Shouldn’t Use Amazon RDS for your SQL Server Databases

Disclaimer: I’ve a Microsoft MVP and shareholder, but neither of these things affected my opinions in this post.

Cloud vendors have built a rich array of platform as a service (PaaS) solutions on their platforms. They market these heavily, because they have higher degrees of stickyness compared to IaaS platforms (and in many cases they likely have higher profit margins), but they also have key benefits to the users of the platform. Because a PaaS solution is fully managed by the cloud provider, they tend have a set of common features:

  • Easy to deploy–you are never running setup.exe
  • Built-in high availability–no need to configure a cluster
  • Easy disaster recovery/geo-replication–usually in most services it’s just a few clicks away
  • Automated backups
  • Automated and possibly zero downtime patching

While some services include other really useful features (for example the query data collected by the Azure SQL Database and Managed Instance platforms), I wanted to focus on the common value adds to PaaS systems across providers. I made the last two of these bold, because I feel like they are are the most important, especially in scenarios where the vendor doesn’t own the source to the applications. Like Amazon RDS for SQL Server.

Amazon RDS Backups

I’m writing this post this week, mainly because of what I just learned this week about the backups for SQL Server on RDS. I was in some client calls this week when I learned the default backup approach is volume snapshots (which I knew), but what I didn’t know what that you couldn’t restore an individual database with these default backups.

I feel like their docs are deliberately vague about this–it’s not clearly obvious that this is the case, but a few Stack Overflow threads and discussions with fellow MVPs confirmed that I was told on the call. Amazon does support you taking your own backups on RDS, and you can then restore individual databases to individual points in time, but where’s that fun (and more importantly the value proposition) in that. To me, this really eliminates one of the biggest benefits of using a PaaS service. AWS refers to normal backup/restore as “Native Backup/Restore” as you are reading docs.

Patching

Azure SQL Database and Managed Instance, both seamlessly patch your databases without your knowledge. For the most part those services utilize hot patching, which means in many cases there isn’t any downtime to install the Azure equivalent of a CU. (Owning the source code has it’s benefits) Amazon RDS can automatically install selected CUs, but you should be aware that is an option when you deploy your instance.


"ValidUpgradeTarget": [
    {
        "Engine": "sqlserver-se",
        "EngineVersion": "14.00.3192.2.v1",
        "Description": "SQL Server 2017 14.00.3192.2.v1",
        "AutoUpgrade": true,
        "IsMajorVersionUpgrade": false
    }

The other thing you should note, is that you may not always have the most current CU available to you. Currently, AWS supports CU12, which is three CUs behind current. However, our customer was only on CU8–so patching doesn’t seem to be as automatic or easy as it is on the Azure side.

Licensing

This one really isn’t AWS’ fault (it’s Microsoft’s fault), but there are a couple of issues with licensing RDS. The first is that you don’t have the option of running Developer Edition for non-production workloads. Which, especially if you are running Enterprise Edition represents an expensive choice–you either need to license Dev/Test for Enterprise, or run Standard Edition in dev to save some money, but not have adequate features in place (though the code platform is mostly the same, performance characteristics can be dramatically different). Additionally, you cannot bring your own SQL Server licenses to RDS, you have to lease them though AWS. Neither of these problems are the fault of AWS, but they still suck.

AWS is an excellent cloud platform, even thought I actively hate their console. For most part a lot of components are very similar or even better than Azure. However, when I comes to a service where Microsoft owns the source code and AWS doesn’t, you can see the clear superiority of Azure. So what is an AWS shop that runs SQL Server to do? IMO, the backup/restore thing is a deal breaker–I would just recommend running in an EC2 VM.

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