Using Differencing Disks with Hyper-V VDI

Storage Container

Pros

Cons

Differencing VHD

*note: dynamic disks face many of the same performance issues that differencing disks face

• Good performance
• Quicker to create than fixed sized VHD
• Grow dynamically to save disk space and provide efficient storage usage
• Smaller VHD file size makes it more nimble in terms of transporting across the network
• Blocks of full zeros will not get allocated and thus save the space under certain circumstances
• Compact operation is available to reduce the actual physical file size

• Interweaving of metadata and data blocks may cause I/O alignment issues
• Write performance may suffer during VHD expansion
• Dynamically expanding and differencing VHDs cannot exceed 2040 GB
• May get VM paused or VHD yanked out if disk space is running out due to the dynamic growth
• Shrinking the virtual capacity is not supported
• Expanding is not available for differencing VHDs due to the inherent size limitation of parent disk
• Defrag is not recommended due to inherent re-directional layer