Somewhere out there! » Kvm

kvm vs qemu-kvm vs kvm-kmod

Nicholas Lee — Thu, 15 Oct 2009 21:01:10 +0000

Ubuntu recently change their package names for kvm. This comment posted on qemu-0.11.0 Released provides an explanation:

qemu-kvm includes features and fixes from upstream qemu and so takes its naming scheme from upstream qemu. You can think of it as qemu optimized for kvm. Note too that qemu-kvm does not include the kernel module but only the userspace and considered to be stable.

kvm-xx on the other hand is the development branch of kvm and not considered to be stable. It’s naming scheme is arbitrary and it also takes features from upstream qemu.

…

kvm-kmod is different to kvm-xx. You can think of kvm-kmod as a subset of the kvm-xx. KVM-xx = userspace + kernel where kvm-kmod is the kernel part of it and qemu-kvm is the userspace part (the guest process itself). You can apply the kvm-kmod to any distro version or linux version.. it’s just the kernel driver. However, without the userspace part, you can’t do much with it.

kvm disk performance with different backends

Nicholas Lee — Mon, 12 Oct 2009 23:16:11 +0000

Here some results from testing I did in August 2009 on KVM with the three different disk image drivers. First a single disk system running Ubuntu x64 9.04:

QCOW2: /dev/vda: Timing cached reads: 9836 MB in 2.00 seconds = 4923.22 MB/sec Timing buffered disk reads: 1050 MB in 3.00 seconds = 349.92 MB/sec

RAW: /dev/vda: Timing cached reads: 10118 MB in 2.00 seconds = 5064.57 MB/sec Timing buffered disk reads: 1054 MB in 3.00 seconds = 351.32 MB/sec

LVM /dev/vda: Timing cached reads: 9328 MB in 2.00 seconds = 4668.90 MB/sec Timing buffered disk reads: 202 MB in 3.00 seconds = 67.26 MB/sec

qcow2,488M,61454,88,288839,43,61540,14,45880,57,445361,57,13550.6,99,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++ raw ,488M,54972,86,54393,16,60636,17,68490,84,442091,43,6685.1,97,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++ lvm ,488M,58248,90,62764,17,58271,19,64677,83,455263,38,7912.3,96,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

QCOW2 Version 1.03c ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP vm2 488M 61454 88 288839 43 61540 14 45880 57 445361 57 13551 99 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ vm2,488M,61454,88,288839,43,61540,14,45880,57,445361,57,13550.6,99,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++


RAW
Version 1.03c       ------Sequential Output------ --Sequential Input- --Random-

-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--

Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP

vm2            488M 54972  86 54393  16 60636  17 68490  84 442091  43  6685  97

------Sequential Create------ --------Random Create--------

-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--

files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP

16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++

vm2,488M,54972,86,54393,16,60636,17,68490,84,442091,43,6685.1,97,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

LVM Version 1.03c ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP vm2 488M 58248 90 62764 17 58271 19 64677 83 455263 38 7912 96 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ vm2,488M,58248,90,62764,17,58271,19,64677,83,455263,38,7912.3,96,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

Then a spreadsheet with a large set of test using Ubuntu x64 9.04 host with two ES SATA disks and LVM over raid1/md.

vmbuilder, virtio and fstab

Nicholas Lee — Fri, 14 Aug 2009 00:26:06 +0000

nic@vm-base:~$ sudo blkid /dev/vda2

/dev/vda2: UUID=”0c75b2dd-6c6f-4729-b041-0d95475dc171″ TYPE=”swap”

If you install a vm with vmbuilder without virtio the swap section of /etc/fstab will use /dev/sda2 instead of /dev/vda2. You can use blkid

nic@vm-base:~$ sudo blkid
/dev/vda1: UUID="bac299c4-c545-46ca-aed3-26da4a56f6d7" TYPE="ext3"
/dev/vda2: TYPE="swap" UUID="0c75b2dd-6c6f-4729-b041-0d95475dc171"
/dev/vdb: UUID="jIkLcQ-zXUo-KIWR-zvmm-cpKP-9PpT-eE9RY3" TYPE="lvm2pv"

and then add this UUID to fstab:

nic@vm-base:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#                                                
proc                                            /proc           proc    defaults        0       0
/dev/sda1                                       /               ext3    defaults        0       0
UUID="0c75b2dd-6c6f-4729-b041-0d95475dc171"     swap            swap    defaults        0       0

in order to get swap working with different driver types.

Running KVM

Nicholas Lee — Wed, 12 Aug 2009 21:50:45 +0000

I’ve started running KVM recently and I’ll post a review at some point. I’m finding it very flexible and much much easier to use that Xen.

There are still a few questions regarding file caches and disk images. In general I’m happy that it’s ready for production.

Redhat and KVM

Nicholas Lee — Fri, 05 Sep 2008 02:54:12 +0000

Redhat has acquired Qumranet the developers of KVM. Will be interesting to see how this plays out in the Linux virtualisation world.

I haven’t tried KVM yet as I’ve been too busy and Xen is more mature – but many of the accounts I’ve read seem to indicate that for Linux its performance is very good maybe better in some cases than Xen. Management is another issue, but that is just a matter of time and development enegry.

From lwn.