Chapter 7. Block I/O
Chapter 7. Block I/O This chapter covers optimizing I/O settings in virtualized environments. 7.1. 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: To set a virtual machine's <blkio> parameters, use the virsh blkiotune command and replace option values according to your environment: Parameters include: weight The I/O weight, within the range 100 to 1000. Increasing the I/O weight of a device increases its priority for I/O bandwidth, and therefore provides it with more host resources. Similarly, reducing a device's weight makes it consume less host resources. device-weights 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. config Add the --config option for changes to take effect at boot. live Add the --live option to apply the changes to the running virtual machine. Note The --live option requires the hypervisor to support this action. Not all hypervisors allow live changes of the maximum memory limit. current Add the --current option to apply the changes to the current virtual machine. For example, the following changes the weight of the /dev/sda device in the liftbrul VM to 500. Note Use the virsh help blkiotune command for more information on using the virsh blkiotune command.
virsh blkiotune virtual_machine virsh blkiotune virtual_machine [--weight number ] [--device-weights string ] [--config] [--live] [--current] virsh blkiotune liftbrul --device-weights /dev/sda, 500