Aspects of the subject matter described herein relate to a buffer pool for a database system. In aspects, secondary memory such as solid state storage is used to extend the buffer pool of a database system. Thresholds such as hot, warm, and cold for classifying pages based on access history of the pages may be determined via a sampling algorithm. When a database system needs to free space in a buffer pool in main memory, a page may be evicted to the buffer pool in secondary memory or other storage based on how the page is classified and conditions of the secondary memory or other storage.