[Users] Heavy Disk IO from a single VM can block the other VMs on the same host

[Hubert Krause]

Hello,

my environment is a Debian squeeze host with a few debian squeeze
guests. The private and root filesystems of the guest are locatet on
the same raid device (raid5) in an luksCrypt Container in an LVM
container on an ext4 partition with nodelalloc as mountoption. If I run
the tool stress:

stress --io 5 --hdd 5 --timeout 60s (which means fork 5 threads doing
read/write access and 5 threads doing constantly fsync) the
responsivness of the other VMs is very bad. That means, Isolation for
IO operations is not given. I've tried to reduce the impact of the
VM with 'vzctl set VID --ioprio=0'. There was only a
minor effect, my application on the other VM where still not
responsive.

Any Idea how to prevent a single VM to disturb the other VMs regarding
diskIO?

Greetings

Hubert