[SOLVED] Qcow2 on btrfs?

[MadMage999]

I noticed while editing a vm on virtual machine manager that the disk was automatically set to qcow2 format.

I'm using btrfs as my only filesystem and I wondered how well qcow2 would perform with regard to the fragmentation issues associated with VMs on btrfs?

[MadMage999]

Is qcow2 basically the same thing that virtual box calls "dynamically sized"?

[dibl]

BTRFS is a marvelous filesystem for general data storage and is fine to support an OS, but probably not your best choice for hosting VMs. This is 3 years old now but I don't think the basic facts and technologies have changed much:

http://www.ilsistemista.net/index.ph...n.html?start=1

Go to the "Conclusions" page where you will read this:

For VMs storage, stay well away from BTRFS: not only it is marked a “Tech Preview” from RedHat (read: not 100% production ready), but it is very slow when used as a VM images store.

Other info: https://www.linux-kvm.org/page/Qcow2

Is qcow2 basically the same thing that virtual box calls "dynamically sized"?

Not "the same as". Dynamic resizing is a feature of qcow2, but not exclusively, and it is not the only characteristic.

[MadMage999]

Okay, thank you.

If btrfs can't be used for VMs,what's the best way to set up a VM host with raid 0? mdadm? As far as I can see kubuntu doesn't install to mdadm (I tried to installer crashed).

[dibl]

I can only tell you what is best for me -- your requirements and equipment may not be similar to mine. I have about 650 GB of user data that I want to have on a very secure hard drive setup, running 24/7/365, and I also have a 50 GB VM that I use almost daily. So, I built a desktop system that has a Samsung EVO 860 SSD, and a pair of WD 1003 hdds on the SATA 3 bus. The SSD is partitioned into 4 partitions, EFI, OS, swap, and /home. The OS and the /home partition are formatted ext4, and my VM lives on the /home partition. The pair of WD 1103 hdds are formatted BTRFS and mounted at /mnt/DATA. I used btrfs defaults, which results in striped data and mirrored metadata, and it uses lzo compression. It's plenty fast and pretty secure (I've been using this setup for about 6 years now -- this is my third pair of WD drives). So btrfs is doing what it is good at, and ext4 is doing the rest.

[oshunluvr]

I haven't done any research or testing of cow2. My solution is to host my VMs on an EXT4 partition.

[dibl]

I use qemu/KVM. The VM image is a .img file, but the virtual filesystem that runs is qcow2. And since the VM is a Windows 10 OS, it thinks it is on NTFS. Is that complicated enough?

[MadMage999]

I'm an enigma, wrapped in a cipher... smothered in secret sauce.