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Editorial Team
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Asked: 2026-06-18T21:46:58+00:00

I am busy migrating to Azure Virtual Machines. Should my SQL Server database MDFs

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I am busy migrating to Azure Virtual Machines.

Should my SQL Server database MDFs reside on the OS disk or on a data disk (which, as far as I understand, is a page blob – also known as a Azure Disk Drive)?

I would have thought the data disk was the correct place, but I’ve just read here that it is slower than the OS disk.

Furthermore, if I use a data disk then should the OS disk and data disk belong to the same storage account container for increased performance?

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  1. Editorial Team

    The short answer is that you want to use Azure Data Drives.

    Longer answer with explanation:
    There are two models for persistent storage in Azure:
    Azure Drives & Azure Data Disks

    They have some common features but there are some differences.

    For both cases, they are backed by a PAGE Blob. The maximum size is 1TB per drive.

    Where they differ is how they are exposed to the VM & communication paths.

    Azure drives was the first implementation and was designed to allow Web/Worker/VM Roles to mount a blob as persistent storage with access via NTFS (i.e. allow legacy PaaS apps to interact with Blob storage without changes). They are implemented as a filter driver that runs inside of the Guest VM.

    Azure Data Disks are part of the IaaS feature set. They are exposed to the Guest VM as a SCSI drive – so you can have multiple drives & create stripe sets for better performance.

    For a detailed description & additional links/instructions/scripts

    http://msdn.microsoft.com/en-us/library/windowsazure/jj672979.aspx

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