NTFS Allocation Unit Size

Question

When we use hyper-v what should i select for NTFS allocation unit size when formatting the disk for store the vhd files? As i know the VHD will have larger file size, so higher NTFS allocation unit size will increase the performance?

Answer 1

Hello,

Thank you for posting in Q&A forum.

Generally speaking, if you expect to store large files, such as VHD files, choosing a larger NTFS allocation unit size (such as 64KB or larger) may be more suitable. This can better utilize disk space, reduce disk fragmentation, and improve file read and write performance.

Best regards，

Jill Zhou

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Answer 2

Hello,

When formatting a disk for storing VHD files in Hyper-V, it is recommended to use a larger NTFS allocation unit size, such as 64KB. This is because VHD files are typically large and using a larger allocation unit size can improve performance by reducing the number of clusters needed to store the file. However, it is important to note that using a larger allocation unit size may also result in wasted space for smaller files. Ultimately, the decision on what allocation unit size to use should be based on the specific needs and usage patterns of your environment.

https://techcommunity.microsoft.com/t5/storage-at-microsoft/cluster-size-recommendations-for-refs-and-ntfs/ba-p/425960

Best Regards,

Hania Lian

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