# Batch Size

The `-b` (or `--batch-size`) option allows commands to be executed on only a specified number of minions at a time. Both percentages and finite numbers are supported.

    salt '*' -b 10 test.version

    salt -G 'os:RedHat' --batch-size 25% apache.signal restart

This will only run test.version on 10 of the targeted minions at a time and then restart apache on 25% of the minions matching `os:RedHat` at a time and work through them all until the task is complete. This makes jobs like rolling web server restarts behind a load balancer or doing maintenance on BSD firewalls using carp much easier with salt.

The batch system maintains a window of running minions, so, if there are a total of 150 minions targeted and the batch size is 10, then the command is sent to 10 minions, when one minion returns then the command is sent to one additional minion, so that the job is constantly running on 10 minions.

Added in version 2016.3.

The `--batch-wait` argument can be used to specify a number of seconds to wait after a minion returns, before sending the command to a new minion.