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7.2. Block I/O Tuning

The virsh blkiotune command allows administrators to set or display a guest virtual machine's block I/O parameters manually in the <blkio> element in the guest XML configuration.
To display current <blkio> parameters for a virtual machine:
# virsh blkiotune virtual_machine
To set a virtual machine's <blkio> parameters, refer to the following command and replace values according to your environment:

# virsh blkiotune virtual_machine [--weight number] [--device-weights string] [--config] [--live] [--current]
Parameters include:
The I/O weight, within the range 100 to 1000.
A single string listing one or more device/weight pairs, in the format of /path/to/device,weight,/path/to/device,weight. Each weight must be within the range 100-1000, or the value 0 to remove that device from per-device listings. Only the devices listed in the string are modified; any existing per-device weights for other devices remain unchanged.
Add the --config option for changes to take effect at next boot.
Add the --live option to apply the changes to the running virtual machine.


The --live option requires the hypervisor to support this action. Not all hypervisors allow live changes of the maximum memory limit.
Add the --current option to apply the changes to the current virtual machine.


See # virsh help blkiotune for more information on using the virsh blkiotune command.