What is the test for a claim of deliberate indifference to health and safety by a prison official?

The Eighth Amendment prohibits state actors from acting with deliberate indifference to an inmate's health or safety. See Farmer v. Brennan, 511 U.S. 825 (1994). A claim based on deliberate indifference to health or safety has two elements. First, an inmate must show that he was "incarcerated under conditions posing a substantial risk of serious harm." Id. at 834. Second, the inmate must show that defendants acted with "deliberate indifference" to that risk. Id. Deliberate indifference is shown by proof that a prison official was "both aware of facts from which the inference could be drawn that a substantial risk of serious harm exists" and that he drew the inference. Id. at 837.