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Poor performance with Storage Space Volume

    Question

  • Hello,

    I'm running a D3 Virtual Machine with 4x1TB data disks provisioned with hostcaching set to 'none'.  We have created a storage pool with the following parameters:

    VirtualDisk: Interleave 65536; NumberofColumns 4; ResiliencySettingName simple; UseMaximumSize.

    InitializeDisk: -Partitionstyle GPT -PassThru

    Format: AllocationUnitSize 65536

    We've run IOMeter to test the IOPS and Throughput.  Results are as expected with the C: Drive (500IOPS 25MBPS) as well as the SSD Temporary Drive.  With the data disks however, we are receiving only 40 IOPS, and 1.7MBPS with an average I/O Response time of 24ms.  We have a dedicated storage account running for these data disks and are not even close to the storage account limits for usage.

    I've tested on other machines in other subscriptions with other storage accounts with similar configurations and found the same result.  The original intention was to use these data disks for increased performance but the C: drive is performance 10x better which shouldn't be the case. 

    All this being said, I am pretty new when it comes to IOMeter but these results are consistent with what the users are complaining about. 

    Wednesday, July 8, 2015 8:30 PM

Answers

All replies

  • Hi Jason,

    Is it a Windows VM / or a SQL VM ?

    If you have no important data in the D: (temporary drive), you can resize the VM to a more larger ( ex : D4 ) one to see if the issue persists.

    Regards,

    Shirisha Paderu

    Thursday, July 9, 2015 3:23 PM
    Moderator
  • Hi Shirisha,

    It is a Windows VM with SQL 2014 Ent. installed from Volume Licensing.  I will try resizing to see how that impacts performance. 


    JM

    Thursday, July 9, 2015 3:48 PM
  • Hi Jason,

    Apologies for the misunderstanding. I was assuming datadisks as a temporary drive ( D:/ ) . But I think you are actually talking about the storage drive ( Data disks ) and not the temporary D:/ drive.

    I recommend using Azure throughput to check the performance and compare if it gives the same results.

    Here is one of the documents on " best practices for SQL performance on Azure VMs " that might help.

    Performance Guidance for SQL Server in Windows Azure Virtual Machines

    Regards,

    Shirisha Paderu

    Thursday, July 9, 2015 4:24 PM
    Moderator