On Wednesday, 17 June 2020 07:32:10 BST J. Roeleveld wrote: > On Wednesday, June 17, 2020 7:42:30 AM CEST n952162 wrote: > > On 06/17/20 06:48, J. Roeleveld wrote: > > > On Tuesday, June 16, 2020 11:08:23 PM CEST n952162 wrote: > > >> On 06/16/20 22:36, J. Roeleveld wrote: > <snipped> > > > > I have not come across MS HyperV outside of small businesses that need > > > some > > > local VMs. These companies tend to put all their infrastructure with one > > > of > > > the big cloud-VM providers (Like AWS, Azure, Googles,...) > > > > > > -- > > > Joost > > > > Thank you for this excellent survey/summary. It tells me that vbox is > > good for my current usages, but I should start exposing myself to Xen as > > a possible migration path. > > I would actually suggest to read up on both Xen and KVM and try both on > spare machines. > See which best fits your requirements and also see if the existing > management tools actually do things in a way that you can work with. > > My systems have evolved over the past 25-odd years and I started using Xen > to reduce the amount of physical systems I had running. At the time, VMWare > was expensive, KVM didn't exist yet and was missing some important features > for a few years after it appeared (not sure if this exists yet, not found > anything about it on KVM): > - limit memory footprint of host-VM during boot. > - Dedicate CPU-core(s) to the host > > Limiting the memory size is important, because there are several parts of > the kernel (and userspace) that base their memory-settings on this amount. > This is really noticable when the host thinks it has 384GB available when > 370GB is passed to VMs. > > Dedicating CPU-cores exclusively to the host means the host will always have > CPU-resources available. This is necessary because all the > context-switching is handled by the host and if this stalls, the whole > environment is impacted. > > For a lab-system, I was also missing the ability to save the full state of a > VM for a snapshot. All the howto's and guides I can find online only talk > about making a snapshot of the disks. Not of the memory as well. Especially > when used to Virtualbox, you will notice this issue. When only snapshotting > the disk, your snapshot is basically the state of when you literally pulled > the plug of your VM if you want to restore back to this. > > For KVM, I have found a few hints that this was planned. But I have not > found anything about this. Virt-manager does not (last time I looked) > support Xen's functionality of storing the memory when creating snapshots > either. Which is why I don't use that even for my lab/testing-server.
As far as I know QEMU with KVM can take snapshots of the current state of RAM, disk(s), CPU - it can take snapshots of images while online. https://wiki.qemu.org/Features/Snapshots2 However, I've only taken snapshots of qcow2 images after I shut down the VM. These work as advertised and they are quite handy before major updates/ upgrades as temporary backups. > As for tips/tricks (below works for Xen, but should also work with KVM): > > The way I create a new Gentoo-VM is simply to create a new block-device > (Either LVM or ZFS), do all the initial steps in the chroot from the host > and when it comes to the first-reboot, umount the filesystems, hook it up > to a new VM and start that. > > Because of this, I can update the host as follows: > - create new "partitions" for the host-system. > - Install the latest versions, migrate the config across > - reboot into the new host. > > If all goes fine, I can clean up the "old" partitions and prepare them for > next time. If there are issues, I have a working "old" version I can quickly > revert to. > > -- > Joost I've wanted to migrate a qemu qcow2 image file or two of different OS', all currently stored on an ext4 partition on my desktop, to a dedicated partition on the disk. Would this be possible - how? Would I need to change the qcow2 to a raw image?
signature.asc
Description: This is a digitally signed message part.
