I started seeing this error on a bunch of my servers:
Event ID 906:
HealthService (2232) A significant portion of the database buffer cache has been written out to the system paging file. This may result in severe performance degradation.
See help link for complete details of possible causes.
Previous cache residency state: 100% (3852 out of 3852 buffers) (20636 seconds ago)
Current cache residency state: 2% (92 out of 3912 buffers)
Current cache size vs. target: 99% (29.344 / 29.414 MBs)
Physical Memory / RAM size: 8191.016 MBs
I see people mention this event when related to Exchange, but these servers are not Exchange servers.