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Jonas's avatar
Jonas
Copper Contributor
Aug 29, 2023

About Azure SQL Database

Hi, how are you?
 
I wonder if you can help me to understand something about Azure SQL Database in the Azure Calculator. This is:
 
 
I have read extensively here and here. 
I understand that Min and Max vCores is the range in wich the compute will be scaled and billed, but I can get:
 
  1. CPU Used
  2. Memory Used
  3. Duration. ¿Is this the auto pause delay (link)?
I hope you can help me to understand
 
Best regards
 
Jona
"azure"
AZURE SQL data base
  • LainRobertson's avatar
    LainRobertson
    Aug 31, 2023

    Jonas 

     

    So, there's two states which mean different things for the compute resources (CPU and memory):

     

    1. The SQL "serverless" service is running;
    2. The SQL "serverless" service is stopped (which is called "auto-paused").

     

    The SQL service is running

    • This is like when a computer is switched on, meaning you are paying for using CPU, memory and storage;
    • If the SQL workload is light, the amount of memory and CPU will likely be towards the lower value limits you entered on the configuration page, which translates into a lower bill when it comes time to pay (since you only pay based on utilisation);
    • If the workload is busy, the amount of memory and CPU will likely be towards the upper limits you entered on the configuration page;
    • If there's no SQL workload at all for the timeframe specified as the "duration" on the configuration page, then the SQL "serverless" service is stopped (called "auto-paused").

     

    The SQL service is stopped (auto-paused)

    • This is like when you shut down a computer;
    • CPU and memory are no longer being used as the SQL instance is effectively "switched off";
    • This means you are saving money, as Microsoft isn't billing you for CPU or memory as the SQL instance is "switched off";
    • You are still charged for storage while the instance is switched off;
    • You don't have to "turn the SQL instance back on" again, as that will happen automatically once any kind of workload tries using the SQL instance again (although there will be a delay and things will run a bit slower for a short while after it starts itself back up again).

     

    Cheers,

    Lain

  • LainRobertson's avatar
    LainRobertson
    Silver Contributor
    Aug 30, 2023

    Jonas 

     

    The duration is a window of time in which the database will be auto-paused if the following two conditions are true for the full duration of that window:

     

    • Number of sessions = 0; and
    • CPU = 0 for user workloads.

     

    So, if you had a really short duration value of 3,600 (one hour), then if the number of sessions remains at zero for an hour, and the user CPU utilisation also remains at 0 for that hour, the database will be auto-paused.

     

     

    Cheers,

    Lain

    • Jonas's avatar
      Jonas
      Copper Contributor
      Aug 30, 2023

      Thanks LainRobertson 

       

      ¿What about the other two options? That is CPU Used and Memory Used. I get confused with these two, because we are talking about a scaling serverless tier that in theory doesn't have provisioned a fixed CPU or Memory

       

      Best regards

      • LainRobertson's avatar
        LainRobertson
        Silver Contributor
        Aug 30, 2023

        Jonas 

         

        Hey, Jonas.

         

        "Serverless" isn't the best term as it can be a bit misleading. The servers are still there, of course, but the difference between the two relevant tiers - "serverless" and "provisioned" is how Microsoft bills you for them.

         

        Starting with the "provisioned" tier - which is more familiar to most people since it's very much the same as a traditional server, you choose how much compute (notably, CPU and memory) and it's always there, and always "on", which in turn means you're always being charged - and at a fixed rate.

         

        In contrast, the "serverless" tier requires that you specify minimum and maximum values for the compute, and additionally asks you for the "duration" it should wait before turning the service "off". This carries the following cost benefits:

         

        • The fewer resources being used, the less you're being charged;
        • When the service is "auto-paused" (or off, if you prefer), you're not being charged for the the compute elements (CPU and memory), meaning you're only paying for storage (since that's always in use.)

         

        There's performance considerations as well when deciding between provisioned and serverless, but the relationship between CPU, memory and auto-pausing is a cost relationship.

         

        Here's some succinct summaries:

         

         

        Cheers,

        Lain

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