Google’s services are generally very reliable, especially considering the scale of the user base and the complexity of some of the applications. Inevitably, though, gremlins occasionally strike and one or more services can suffer slow response, odd behaviour or unavailability.
The first place to look is at Google’s own Apps Status Dashboard:
You can use the Apps Status Dashboard to check on the current service status of individual services such as Gmail, Google Calendar, Talk, Drive, Sheets and so on. Any service exhibiting abnormal behaviour is shown as a coloured entry on a graphic display. The figure below shows the existence of a brief (and now resolved) issue with Google Drive, and an ongoing issue with Admin Console:
Hover over the graphic display of a fault to display brief details of the issue:
You can also click the graphic to get a new page with full chronological details of the issue history and status:
Scroll down on the initial Status Dashboard display to see similar status details on some further Google services not covered by the Google service level agreement: