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I have some Hyper-V VMs which are dynamic disks. I want to convert them to basic for the sake of online VSS backups. I know that this conversion in Windows (if the option was not greyed out in the VMs for me...) requires a format of the HD/loss of all data. Products like claim to do this with no data loss. Is this really possible? Is there a way to do what I want with no data loss?


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Are you referring to basic vs. dynamic disks in Windows or dynamic vs. fixed disks in Hyper-V (the VHD)? – user94471 Sep 12 '11 at 17:40

Your question has nothing to do with Hyper-V. This aspect of a machine's behavior doesn't change when you make it virtual.

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I have done this on a physical machine using Paragon Partition Manager.

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I have successfully done this with Acronis Disk Director - Good luck!

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How much of a 'no data loss' guarantee are you after? I think any reputable converter software will tell you to back things up before trying, 'just in case'. And the absence of such a warning should be taken as evidence of bad documentation, not good software.

Having said that, read this microsoft knowledgebase article. Read the workaround section, don't just look at the title and assume I've given you a bad link. That's pretty much what any software is going to be doing behind the scenes, I'm sure. But you'd be mad to try this (or any of the software) without a full backup. And if you've got that then you're most of the way to the official 'backup, recreate partition, restore data' answer anyway.

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