In public cloud computing, the notion of platform as a service, is an offering that offers some key computing concept, as a service. Since you are reading my blog, you are probably most familiar with Azure SQL Database (which if you are old like me, you might call SQL Azure). Azure SQL Database for the uninitiated is Microsoft’s database as a service offering. You make a few mouse clicks or run a few lines of code, pay some money to Microsoft, and you have a database for your application. Microsoft handles your software installation, your settings, backups and restores, and numerous other operational tasks and lets you write your code.
Azure SQL Database’s original pricing model simply referred to a number called database throughput/transaction (Microsoft really likes to rename things if you haven’t noticed) units, or DTUs, which are a blended measure of CPU, memory, and read/write IOPs. A pricing model like this allows the cloud provider to abstract the underlying hardware, which is another simplification of the cloud model. However, especially in the early days of the public cloud, this concept was hard for IT orgs (many, at the time were still buying physical hardware) to grasp.
Different PaaS offerings offer different levels of abstraction, though they do have a few things in common. You are almost never going to install software—patching and installation are nearly always handled by the vendor. However, with some different offerings you may be doing things like configuring storage and networks—a good example of this is with the new SQL Server offering—Managed Instance. This excellent post from the SQLCAT team shows the complexity of sizing data files to get maximum performance out of the underlying storage. Doing this requires a really firm understanding of Azure storage and how it works on the platform. You also need to know a little bit about virtual networking, because you will need to get your managed instance “wired” into a network where it can talk to your application.
Another difference with Managed Instance is that, you choose a tier, General Purpose, or Business Critical (which affects your storage performance and availability) and then the number of cores you would like, and the generation of hardware you would like. While Azure SQL Database is also moving to this model, it is just noteworthy to see the difference in abstraction. I like to think of this as a curve that has pure infrastructure as a service (IaaS) on one side (VMs in the cloud) and software as a service (SaaS) like Office 365 on the other side. Managed instance is definitely closer to the IaaS side of things.
Another thing you want to verify is, the backup situation for your chosen service. While most services do backups (and you may not even have the option to do your own backups, like in Azure SQL DB), it is important to know what your data loss SLA and what your options are if there’s an outage or a disaster.
I was inspired to write this post, because while delivering training last week, I deployed a new Azure Databricks cluster, and I was totally blown away at how simple the deployment process was—you had two performance options (for advanced deployments you could choose more changes), but it was dead simple from a deployment perspective. I don’t think it’s a good thing or a bad thing that different services have different levels of configuration—I think in some services you need that, but sometimes it’s nice just to have a box that does a service for you.