Add HDDACCESS and WRITEBACK metric

- Cache average access time for write-back policy
- HDD average access time using RPM and head-seek time

hddaccess

@@ -0,0 +1,7 @@
+#!/bin/python
+
+rpm = int(input("RPM? "))
+headseek = int(input("AVG head seek? (ms) ")) # ms 
+rotlat = 60/rpm/2 * 1000 # ms
+print(headseek+rotlat)
+

writeback

@@ -0,0 +1,10 @@
+#!/bin/python
+
+perchit = float(input("PERCENT HIT? "))
+percw = float(input("PERCENT WRITE? "))
+cacher = int(input("CACHE READ TIME? "))
+cachew = int(input("CACHE WRITE TIME? "))
+memr = int(input("MEM READ TIME? "))
+memw = int(input("MEM WRITE TIME? "))
+
+print(perchit*percw*cachew + perchit*(1-percw)*cacher + (1-perchit)*percw*memw + (1-perchit)*(1-percw)*memr)