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Boot to VHDX with Windows 8 with SSD Trim

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#1 TwoScoops



  • Joined: 17-May 11

Posted 02 July 2013 - 21:32

I recently downloaded the Windows 8.1 preview iso and decided to install it to a VHDX and boot directly from that. (Doing this is fantastic as it means your whole system is installed into one moveable file with all the virtualisation benefits that go with it - and some of the drawbacks) This VHDX is stored on one of my platter based secondary HDDs [D: drive], and worked perfectly.
My main installation of Windows 8 is installed directly to my primary SSD [C: drive] (not in a VHDX file).
Coincidentally, I needed to reinstall Windows 8 on my SSD (was having trouble with it - now done) and so since the Windows 8.1 preview installation and boot to/from VHDX worked so well, I decided to prepare a fresh installation of Windows 8 into a VHDX file on my D: drive and planned on moving that VHDX file to my SSD which I would format and prepare first.
My question is: If I move the Windows 8 VHDX file (and some differencing VHDX files) to my freshly formatted SSD, will TRIM make it's way through to the SSD (and work?) so as to avoid degraded SSD performance over time or excessive writes to the drive?
I've researched this as well as I can (Google!) and there seems to be no definitive answer to this question surprisingly. I know it's quite a niche scenario and seemingly unsupported but it's intriguing and useful enough to warrant further investigation.
Officially, VHDX files support TRIM in certain situations when used with the Hyper-V software directly, but there isn't a clear answer I can find anywhere as to whether SSD Trim functionality is supported or available when VHDX files are used to boot directly from an SSD.
I've found a blog (http://www.jaylee.or...HDX-format.aspx) that suggests that TRIM works but it's not definitive - they seem to just guess. Anyone here know for sure? Or know where I can find out?
Also - anyone know of any other downsides to booting from VHDX on an SSD (or just in general) over a direct installation to the disk?