## Exercise 17: Estimating Data Access Times

Adapted from Exercise 9.5 (Ramakrishnan & Gehrke): Consider a
disk with a sector size of 512 bytes, 2000 tracks per
surface, 50 sectors per track, five double-sided platters,
and an average seek time of 10 msec.

- What is the capacity of a track in bytes ? What is the
capacity of each surface ? What is the
capacity of the disk ?
- How many cylinders does the disk have ?
- Give exampes of valid block sizes. Is 256 bytes a valid
block size ? 2048? 51,200?
- If the disk platters rotate at 5400 rpm (revolutions per
minute), what is the maximum rotational
delay ?
- If one track of data can be transferred per revolution,
what is the transfer rate ?
- If block size is 3072 bytes, and a DBMS page is 3072
bytes, what is the average I/O time to
fetch a random page from disk ?
- Suppose an employee table is stored in 8 pages and these
8 pages are laid out contiguously on
disk on the same track. What is the I/O time required to
perform a point query on employee if
the data is not sorted ?
- What is the I/O time required to perform a point query if
the data is sorted according to the
query condition ? (You may assume that only one initial seek
is required).