The mysqlbackup command has settings to for the number of read, write and process threads. The defaults are 1 read, 1 write and 6 process threads. So that isn't really useful for throttling as I was using the defaults.
Using the ionice utility wouldn't work as that requires the CFG I/O scheduler.
I found a solution in this blog post. It is to use cgroups on Linux. I had used cgroups before to test how a galera setup works when one of the three servers had a much slower CPU.
# mkdir /cgroup/blkio # mount -t cgroup -o blkio non /cgroup/blkio # cgcreate -g blkio:/mysqlbackup # ls -lh /dev/mapper/vgdb01-lvdb01 lrwxrwxrwx 1 root root 7 Sep 26 14:22 /dev/mapper/vgdb01-lvdb01 -> ../dm-2 # ls -lh /dev/dm-2 brw-rw---- 1 root disk 253, 2 Sep 26 14:22 /dev/dm-2 # cgset -r blkio.throttle.read_iops_device="253:2 20" mysqlbackup # cgset -r blkio.throttle.write_iops_device="253:2 20" mysqlbackup # echo $$ > /cgroup/blkio/mysqlbackup/tasks # cat /proc/$$/cgroup 1:blkio:/mysqlbackup # mysqlbackup --user=root --password=xxxxxx --with-timestamp --backup-dir=/data/backup backup
This worked exactly as I had hoped and expected. Both read and write operations were limited to 20 iops.
It turned out to be a issue with the storage system, so I won't have to use this in production but I hope that this will be to value of someone. This can also be useful in other situations.
