Estimates used.

During simulation we had to estimate the costs for reading a page from disk or writing it to disk. We conservatively assumed that writing ``dirty'' pages to disk incurs no cost at all, to compensate for file systems that keep low the cost of multiple writes (e.g., log-structured file systems). Additionally, we assumed a disk with a uniform seek time of 5ms. Admittedly, a more complex model of disk access could yield more accurate results, but this should not affect the validity of our simulations (a 5ms seek time disk is fast by modern standards). In Section 4.3 we examine the effect of using a faster disk (up to a seek time of 0.625ms).