• KVM. What is so good about it?
    16 replies, posted
I have been toying around with KVM a couple of times and it does not really deliver the promised speed gains I have read about. Compared to Virtualbox, KVM is just horribly slow and installing anything took more than three times longer than it should. Am I doing something wrong or is this how it is supposed to be? I am sure that my hardware supports virtualization (Intel E6600) and that I have installed the necessary KVM modules because the "kvm-ok" command reports that everything is A-OK.
Funny, I also have a machine I virtualize with and it uses an E6600. E6600, 3GB of DDR2. I use Proxmox VE, it's basically Debian with Proxmox's software. I use KVM for virtualizing Windows machines and the performance is excellent. I used to have a dedicated Windows Server 2008 R2 machine, but I virtualized it. I can't tell a difference between the two. In my opinion, it's something wrong on your end.
Have you done any Windows specific optimizations? I read something about disabling AHCI could help.
Haven't done any myself, but I can't guarantee that Proxmox doesn't have any special settings for that, since I always set host type to the correct Windows section when creating a VM instead of just letting it be "Other".
It's probably slow because of the disk image you're using. For some reason, Qemu/KVM is hella slow if you use a file as the disk image. If you make a physical partition on your disk image, it's way faster.
i thought this would have been common sense for any vm you wanted performance from
[QUOTE=Roo-kie;28517879]i thought this would have been common sense for any vm you wanted performance from[/QUOTE] Yeah, but somehow Virtualbox gets pretty decent performance using file based disk images. Qemu's performance on that is terrible, like it's not even usable.
Proxmox VE doesn't make actual partitions for the VMs. I guess it must have been compiled with magic.
I installed Windows 7 using KVM into an image. It's not perfect, but it seems to be running pretty well on my subpar CPU (Core 2 Duo E6300) - couple of issues though. I think the graphics drawing is going to the CPU; the mouse movement moves around, and the screen generally tears. The second issue is bridged networking; all the times I've tried it, I end up breaking my connection and having to run dhcpcd to get myself a new IP from my router. Will putting a Windows 7 partition on a hard drive instead of image speed up the graphics drawing?
[QUOTE=Nipa;28605601]I installed Windows 7 using KVM into an image. It's not perfect, but it seems to be running pretty well on my subpar CPU (Core 2 Duo E6300) - couple of issues though. I think the graphics drawing is going to the CPU; the mouse movement moves around, and the screen generally tears. The second issue is bridged networking; all the times I've tried it, I end up breaking my connection and having to run dhcpcd to get myself a new IP from my router. Will putting a Windows 7 partition on a hard drive instead of image speed up the graphics drawing?[/QUOTE] The graphics drawing is always done on the CPU with Qemu/KVM. It doesn't have GPU acceleration. Putting Win7 on it's own partition on the hard drive will drastically increase disk I/O performance however.
Is there any decent virtual machine managers for Linux that have graphics acceleration? I tried VirtualBox, but my system slowed to a crawl while installing Windows 7, and eventually froze - I had to reboot. KVM is working for now, but I suspect the graphics drawing will get to my nerves soon.
VMware Workstation does Direct3D acceleration. It's not perfect, 3D games tend to have graphics glitches, but it works fine for Aero.
Installing Windows in VMWare Workstation as we speak. It's already much smoother! Thank you!
I have done some more testing and have now setup Debian 6. This time everything seems to run quite fast except for disk IO, which is ridiculously slow compared to VirtualBox. I have read about some drivers for Windows but I am not really sure if I need them.
I love VMWare Workstation. It's MINDBLOWINGLY fast. It runs EXACTLY like native Windows, with no performance hit to the host. It's brilliant. I can't recommend it more.
Running Scientific Linux 6 and FreeBSD 8.2 in VMs on my Gentoo install. :smug: Virt-manager is really cool if you get it set up right. I'm going to try getting the networking thing working later, so I can mess with VMs running on my desktop from my laptop. [img]http://i.imgur.com/Ul25W.png[/img]
[QUOTE=Nipa;28614477]I love VMWare Workstation. It's MINDBLOWINGLY fast. It runs EXACTLY like native Windows, with no performance hit to the host. It's brilliant. I can't recommend it more.[/QUOTE] It does have a performance hit sometimes, but it's the most mature PC virtualization product available, AFAIK. I've been using it since 2003. Its main downside is that it's not free. Actually, you might want to try VMware Player, which uses the same virtualization engine as Workstation. It was originally meant to just run VMs that others have created, but in version 3.0 they added the ability to create VMs too, and Player [i]is[/i] free (as in beer, not speech). It lacks some of Workstation's more advanced features, like snapshots and teams, but for basic virtualization without having to spend money or infringe copyright, it's not a bad choice.
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