While “all aspects of storage performance are improving,” they are doing so at
different rates.
They talk about the difference between
the technology ratio
PagesPerMBofRAM / AccessesPerSecondPerDisc
and the economic ratio
PriceOfDisc / PriceOfMBofRam
The Five Byte Rule is now The One Byte rule
Mainframe processors are expensive and thus follow a 10 byte rule
They discuss a rule for sequential access common in sorts and joins
With their assumed numbers they determine one-minute break even point
where it makes sense to cache disc data on main memory if it will be
needed within a minute
RAID
RAID 1 decreases cost of reads a little bit but doubles cost of writes
RAID 5 increases the cost of writes by a factor of 4
Tape
They give numbers for tape versus RAM and tape versus disc
They discuss when buffer managers should checkpoint their state
They also talk about how having hot standbys can change the economics