"I'm happy to announce that I've implemented a Block I/O bandwidth controller," began Ryo Tsuruta, explaining that it was intended to be used in a cgroup or virtual machine environment, implemented as a device-mapper driver. He detailed a token-based implementation in which dm-band passes out to the various groups, "a group passes on I/O requests that its job issues to the underlying layer so long as it has tokens left, while requests are blocked if there aren't any tokens left in the group. One token is consumed each time the group passes on a request. Dm-band will refill groups with tokens once all of groups that have requests on a given physical device use up their tokens." Ryo explained:

"Dm-band is an I/O bandwidth controller implemented as a device-mapper driver. Several jobs using the same physical device have to share the bandwidth of the device. Dm-band gives bandwidth to each job according to its weight, which each job can set its own value to. At this time, a job is a group of processes with the same pid or pgrp or uid. There is also a plan to make it support cgroup. A job can also be a virtual machine such as KVM or Xen."