Looks like that yesterday at around 14:23 our parchercache hosts started to experiment an increase on used disk space.
https://grafana.wikimedia.org/render/dashboard-solo/file/server-board.json?refresh=1m&panelId=17&orgId=1&from=1539149866002&to=1539236266002&var-server=pc1005&var-network=eth0&width=1000&height=500&tz=UTC%2B02%3A00
Not sure what happened the 21st of September in eqiad (it was passive at that time), but these graph is interesting:
https://grafana.wikimedia.org/render/dashboard-solo/file/server-board.json?refresh=1m&panelId=17&orgId=1&from=1536644484669&to=1539236484669&var-server=pc1005&var-network=eth0&width=1000&height=500&tz=UTC%2B02%3A00
https://grafana.wikimedia.org/render/dashboard-solo/file/server-board.json?refresh=1m&panelId=17&orgId=1&from=1536644522112&to=1539236522112&var-server=pc2005&var-network=eth0&width=1000&height=500&tz=UTC%2B02%3A00