This is a problem I've had for three or four years, but never solved. I send a monthly mailing to about 50k contacts using CiviMail. Each mailing is scheduled using the standard CiviCRM job scheduling. All works fine except that during the sending, the templates_c/en_GB folder grows to about 30GB or more, and has to be emptied manually (either from the command line or using the the CiviCRM Clean Up Caches page) to stop the server from running out of disk space. The files and directories which are being created under templates_c/en_GB/ all seem to have plausible permissions (read and write for the Apache user, read only for everyone else), so I don't understand why they're not being cleared.
Can anyone suggest anywhere to start looking for a solution? Thanks.
This happens with the following set-up, but I have had the problem for a long time, with all previous versions as well.