https://tools.wmflabs.org/nagf/?project=integration#h_integration-puppetmaster_disk
There's a constant stream of writes to the disk in this directory, and every few hours it trims (or compresses?), but never back to the same size. It's gradually growing and growing and since the disk is only like 2GB, it's too full.
Notification Type: PROBLEM Service: Free space - all mounts Host: integration-puppetmaster Address: 10.68.16.96 State: WARNING Date/Time: Fri 23 Jan 23:44:42 UTC 2015 Additional Info: WARNING: integration.integration-puppetmaster.diskspace._var.byte_percentfree.value (<30.00%)

