When you create a docker container, by default, I/O on it is unlimited. For my
project I needed to create docker containers with limited I/O bandwidth but
docker does not provide I/O limits out of the box like cpu (--cpuset and --cpu-shares) or memory (--memory) limits. However, the
kernel provides blkio cgroup subsytem which can be used to limit I/O on a block
device.
I created this script which limits I/O bandwidth on containers.
To use the script, create a container and record the container ID. Pass the ID to the script along with the read and write bandwidth (measured in bytes per sec).
$ CONTAINER_ID=$(docker run -d ubuntu sleep 4000)
$ python docker_io_limit.py $CONTAINER_ID --read 1048576 --write 1048576
The above command will give the docker container a read/write bandwidth of 1MB/s. You can verify this by using dd
$ docker exec -it $CONTAINER_ID /bin/bash
root@179768a19696:/# dd if=/dev/zero of=testfile count=10240 oflag=direct
10240+0 records in
10240+0 records out
5242880 bytes (5.2 MB) copied, 6.87569 s, 763 kB/s
root@179768a19696:/# dd of=/dev/null if=testfile count=10240 iflag=direct
10240+0 records in
10240+0 records out
5242880 bytes (5.2 MB) copied, 5.2248 s, 1.0 MB/s
root@179768a19696:/#
As you can see we get about 763 kB/s write and 1.0 MB/s read speed.