It appears as if <email@example.com> wrote:
|Tapes are magnetic media, and tapes are rather slow, perhaps the slowest
|of all computer-related storage technologies. Hard disks (magnetic) and
|CD-ROMs (optical) are somewhat faster than tape, but much slower than
|volatile RAM (DRAM). There is a big operational difference between hard
|disks and CDs on the one hand and tape on the other, and that is that
|tape must be mechanically reeled to the spot where a read or write
|operation is required, so tape has a slow average access time for random
|access, very much slower than disk type geometry.
Mechanic devices (tapes, mechanic disk drives, CDs, etc.) require more time to perform an operation than electrical or pure-magnetic devices do, as they move _atoms_ around. A DRAM device moves _electrons_. Electrons require much less power to move around, as they occupy less space, have much smaller mass, and have a non-zero charge so one can use electrical fields to move them.
So if one compares mechanical devices to a DRAM device, one, figuratively writing, compares apples and nuclear submarines.
Comparing various solid-state devices (like DRAMs and flash disks) make more sense (the comparisons have greater information contents).