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What does the Azure Disk Throughput limit actually represent RRS feed

  • Question

  • Hi,

    I have a DS12v2 Azure VM. Specifications indicate that DS12_V2 has disk through put limits of 12800 IOPS and 192MBps.

    Are the limits related to the entire machine or each individual disk. For example if we have a SQL Data and Log drive and we are inserting records into a table we are writing to both the Data and Log drive so do we get up to 192MBps for each drive or the sum of the two drives.

    Assuming it's each disk (i hope so) if we were to strip two P20s for the Data and Log drives the theoretical throughput is 300 MB/s per disk (2 x 150MBps). As the server itself is rated to cap at 192MBps i'm guessing you'll never reach the 300 MB/s.

    Regards.

    Simon.

    Tuesday, August 22, 2017 10:03 PM

Answers

  • DS12_V2 limits of 12800 IOPS and 192MBps are on VM level, not for each disk.

    In my expirience, performance is usually above this limit, I think that limit is performance that MS guarantees.


    Mustafa Toroman, Azure MVP

    Wednesday, August 23, 2017 6:34 AM

All replies

  • DS12_V2 limits of 12800 IOPS and 192MBps are on VM level, not for each disk.

    In my expirience, performance is usually above this limit, I think that limit is performance that MS guarantees.


    Mustafa Toroman, Azure MVP

    Wednesday, August 23, 2017 6:34 AM
  • DS12_V2 limits of 12800 IOPS and 192MBps are on VM level, not for each disk.

    In my expirience, performance is usually above this limit, I think that limit is performance that MS guarantees.


    Mustafa Toroman, Azure MVP


    Seems strange that Microsoft recommends P30 disks for SQL Server yet at a cap 192MBps they would never be fully utilised. You'd have to throw servers with huge amounts of CPUs which would then be under-utilised.
    Wednesday, August 23, 2017 7:35 AM
  • Unfortunately, that is the case. To fully utilise P30 disk you must use highend VMs, and in most cases you don't need that amount ot CPU and RAM. But to get max IOPS/throughput, you need to use servers with large amount of CPU and RAM.

    Mustafa Toroman, Azure MVP

    Wednesday, August 23, 2017 8:16 AM
  • Yes As Mustafa told, that is VM level. And you are correct if you use stripe disks still you will not get the full performance since there is a CAP.
    Wednesday, August 23, 2017 9:15 AM