Ticket #20233 (new defect)

Opened 5 months ago

Last modified 5 months ago

Unwanted conversion dynamic to fixed disk

Reported by: Codehunter Owned by:
Component: virtual disk Version: VirtualBox 6.1.18
Keywords: Cc:
Guest type: Windows Host type: Linux



I'm unsure about this is a bug or a feature, but I'm very confused about it:

I have a VM with a fixed VDI. This is explicitly what I want to have for some performance issues on Linux host. When I clone this VM via Ctrl-O, I wondering that the clone has an dynamic VDI, I didnt like that behavior.

But really really bad is: The source VM is also converted to a dynamic VDI. Therefore I must go to the vboxmanage modifyvm twice (for source and target VM) and convert it back to fixed. These steps consumes unneccessarily space on my SSD.

Please make an selection in the GUI which target disk type is wanted. And much more important: Please leave the source VM unchanged!

Thanks and Greets!


screenshot_1.png Download (58.8 KB) - added by Codehunter 5 months ago.

Change History

comment:1 Changed 5 months ago by klaus

Please provide evidence... cloning does not modify the source VM or its disk images in any way, at least not at the high level. So I can't believe your claim that the cloning affects the source image variant.

You'll need to provide a lot more information - such as details which clone variant you use. Because if you go for a linked clone (which already hints that there is a special relationship between the VMs, requiring small changes which aren't really visible) then that has to create a snapshot which adds a differencing image to the source VM, which is always a dynamic image (otherwise snapshots would be infinitely expensive). If you do a full clone then the source VM is entirely unchanged.

Regarding the cloned VM: the images should preserve the variant of the source image. This means if you go for a linked clone then the source is a dynamic image, causing the creation of a dynamic image for the target. If you'd do a full clone for a VM with fixed image (and no snapshots) then you'd get a fixed image for the target, too.

If you now want to undo the linked clone creation: delete the linked clone, and also delete the snapshot in the source VM. Otherwise the snapshot stays and that keeps the image source as dynamic, affecting cloning.

It's complex, but unless you provide different facts I assume it's all behaving as designed, and the design has its reasons.

Changed 5 months ago by Codehunter

comment:2 Changed 5 months ago by Codehunter

It was an "full" and not an "linked" clone. See screenshot I have attached now. And please believe me, its true. I think the way was happen is: VBox has converted the source VDI from fixed to dynamic before it was cloned. The clone was dynamic too. The original source disk size before cloning was ~ 100 GiB (fixed) and after cloning ~ 33 GiB (dynamic). The cloned VDI was ~ 33 GiB.

I am very sure that the original VDI before cloning was fixed 100 GiB because I had so many hours of seeking for performance issues a while ago. Therefore I made the conversion from dynamic to fixed and the lags was fixed.

VBox is 6.1.18 r142142 (Qt5.9.5), the Host is Linux Mint 19.3 Cinnamon 4.4.8, the Kernel is, the CPU is a Ryzen 7 2700X, RAM is 32 GiB.

comment:3 Changed 5 months ago by klaus

The screenshot of the wizard is not very helpful - you need to provide details about the source VM. Ideally attach the corresponding .vbox file, because with that I can see if differencing images are present (I can't say from that file if the image is fixed or not, but that's something where you should know best).

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