Which disk format works for an Azure Virtual Desktop session host image?
You have an Azure storage account that contains the generalized Windows 10 disk images shown in the following table. [sampleXML/xmlfile-61_1.png] You need to create an image that will be used to deploy an Azure Virtual Desktop session host. Which disk should you use?
Community Insight
The exam tests whether you know Azure accepts only fixed-size VHD for uploaded VM images, and the trap is assuming the newer VHDX format is automatically valid.
Azure Virtual Desktop session host images must be based on a fixed-size VHD, so the correct disk is the one in VHD format with fixed allocation. This page explains why VHDX disks, even fixed-size ones, require conversion before use.
Choosing Disk3 because VHDX is newer and supports larger disks; however, Azure image upload requires VHD, so a fixed-size VHDX would need conversion first.
Community Discussion (14 comments)
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Expert Analysis
Why the Answer Is Correct
Disk1 is the fixed-size VHD. Microsoft's prepare-for-upload guidance supports generation 1 and generation 2 VMs only when they are in VHD format and use a fixed-size disk, which is the same constraint that applies when you build an Azure Virtual Desktop session host image. A fixed-size VHD can be uploaded and used as an image source without format conversion or dynamic-disk expansion surprises. That makes Disk1 the least administrative work and the option the exam expects. It also matches the community consensus that Disk1 is the answer.Why the Other Options Are Wrong
Disk2 is a dynamically expanding VHD; even though it is VHD, it is not fixed-size, so it does not meet the Azure upload requirement. Disk3 is a fixed-size VHDX; VHDX is not accepted directly and must be converted to VHD first. Disk4 is a dynamically expanding VHDX, so it fails both the format and the fixed-size requirement. Any answer that picks Disk3 simply because VHDX is newer ignores the upload constraint.Community Comment Notes
MarioGaming110's answer emphasizes "VHD Format" and "Fixed Size" as the two selection criteria, which aligns with the Microsoft guidance. tristamm16 pushed back that "You would typically always want to use a VHDX over a VHD", but the linked upload article still requires VHD and fixed-size disks. Magis and DallasM both summarize the rule as fixed-size VHD only, and picho707 notes that VHDX would first need conversion to VHD, adding administrative work. Leocan and lfbustamante likewise converged on Disk1.Official Reference
Exam Strategy
Eliminate options by format first: any VHDX disk requires conversion, so it is not the best answer for an upload-ready image. Then check sizing: Azure expects a fixed-size VHD rather than a dynamically expanding one.
Frequently Asked Questions
Why can’t a fixed-size VHDX be used for an AVD session host image?
Azure’s upload path accepts VHD, not VHDX; a VHDX must be converted to a fixed-size VHD first, so it is not the best disk to select.
What makes Disk1 preferable to a dynamically expanding VHD?
Fixed-size VHDs give predictable performance and match Azure’s supported image format, avoiding conversion and resizing work before deployment.
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