On Wed, Feb 22, 2017 at 10:17:01AM +0200, Mimiko wrote:
Hello.
I already wrote to qemu mail list and didn't find an answer.
I've setup qemu / kvm on Debian Wheezy to host some Debian Jessie guests.
I create disk like this:
virsh vol-create-as --pool default --name root.vhd --capacity 50G --format vpc
Then create a virtual with this:
virt-install --connect qemu:///system \
--ram 2048 \
--vcpus=4 \
--cpuset=auto \
--pxe \
--os-type linux \
--boot network,hd,menu=on \
--disk vol=default/root.vhd,device=disk,bus=virtio,cache=writethrough \
--network=bridge:br0,model=virtio \
--noautoconsole \
--hvm \
--autostart \
--check-cpu
After setting up the system I've got poor disk performance.
Using
time dd if=/dev/zero of=/tmp/test oflag=direct bs=64k count=16000
I get 1048576000 bytes (1.0 GB) copied, 397.473 s, 2.6 MB/s
I've changed cache to writeback and got 20MB/s with this test. But copying a
file to this virtual using samba gives me no more of 2 MB/s.
I've tested network connectivity with iperf and got around 750Mbit/s, which I
think is satisfactory.
I will not want to use raw devices, as it is not self expanded and will use
whole space regardless of how much real data occupy.
libvirtd (libvirt) 0.9.12.3
Is there a way to increase disk speed to at least 50MB/s ?
StackExchange
(http://serverfault.com/questions/407842/incredibly-slow-kvm-disk-performance-qcow2-disk-files-virtio)
suggests that QCOW2 may be a factor, and to use:
$ qemu-img create -f qcow2 -o
preallocation=metadata,compat=1.1,lazy_refcounts=on imageXYZ
but there's a bunch of other cargo-cult options to try, too! :D
--
For more information, please reread.
