Successfully started kvm without libvirt and with additional -drive options:
cache=writeback,aio=native
Copied 1,3GB to windows guest share over GB network with 41MB/s sustained
transfer rate.
Windows and linux Guests are running very smooth again.
Maybe libvirt should use those -drive options
I second this - just incredibly slow I/O results in nearly unusable KVM guests.
Tested with lucid guests and windows 7 using virtio drivers.
I am using a luks crypted lvm partition on top of a sata md raid.
Changing I/O schedulers doesn´t help.
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Slow disk IO for all guests with all disc mode