[prev] 34 [next]

Cost Models (cont)

Since time cost is affected by many factors
  • speed of i/o devices (fast/slow disk, SSD)
  • load on machine
we do not consider time cost in our analyses.

For comparing methods, page cost is better

  • identifies workload imposed by method
  • BUT is clearly affected by buffering
Estimating costs with multiple concurrent ops and buffering is difficult!!

Addtional assumption: every page request leads to some i/o