VMs in BTRFS?

[SpecialEd]

Although I never quite wrapped my head around BTRFS(didn't put too much time or effort into either), I am getting a new laptop to play with and thought I might give it another go. IIRC, it was mentioned that to have VM's in BTRFS you need to set aside a partition in ext4, is that correct?

[oshunluvr]

That is one way to go. The easiest actually. That's what I do, but I'm using a desktop with 5 drives so....

Alternately, you can use FIXED sized VM drives rather than DYNAMICALLY sized. Downside is, obviously, that a 20GB fixed virtual drive consumes 20GB of drive space, where a 20GB dynamically sized virtual drive only consumes needed space up to 20GB.

Finally, you can set NODATACOW on folders or files: http://www.infotinks.com/btrfs-disab...tory-nodatacow

What the best option for you is will depend on what you have drive-wise and your VM needs. I have a lot of them (always playing with one thing or another) but a ton of space so I just dedicate a drive to VMs.

[GreyGeek]

I've been using BTRFS for many years (but not as long as Oshunluver) and I've created several qemu/kvm's over the years. BTRFS allows one to resize the <ROOT_FS> and I did that to shrink it by 60GB. Then I created a 60GB EXT4 partition on which to save my virtual drives. Doing that they can be dynamic as well, since a BTRFS snapshot won't include that partition. When I was done I'd use kpartition to destroy that partition and give it back to the BTRFS partition. Then I'd resize the <ROOT_FS> to maximize it to fit. That would bring my BTRFS back up to its 465GB install size.

I got tired of that and after I installed qemu/kvm I used nodatacow on the vm image storage folder before I created my first VD. I also used only static VDs. So, BTRFS ignores it. If one is going to set aside X GB for VDs on an EXT4 partition that X GB isn't available to BTRFS anyway. Also, I've had no speed or stability issues with my VM's & VD's. They've been lightning fast, especially under Plasma 5. That's one reason why I shifted from using VirtualBox to qemu/kvm. My virtual desktops run about as fast as my main desktop, which is running on top of my GT650M GPU.

[oshunluvr]

For sure QEMU/KVM is faster. I'm amazed how fast some of my VM boot. Even Windows 10.