What is the similarties between memory management fragmentation and disk fragmentation?
Fragmentation is the result of an
inefficient use or allocation of memory space. It is not usually a
catastrophic occurrence, but it can cause problems in operating
efficiency. In both main memory as well as on disk, data is stored
in blocks. The blocks are all uniform in size but the data may or
may not be. In other words, data that doesn't fill up the entire
block ends up wasting space. This is called internal fragmentation.
Alternatively, external fragmentation refers to data that requires
multiple blocks to store, but which can't be contiguously located.
External fragmentation may cause problems in primary storage, but
it's not as big a deal on disk. Data most likely won't load into
primary storage if there are not enough contiguous blocks available
to house it. A disk on the other hand, will accept data in
non-contiguous blocks, but this will cause performance issues. The
disk controller will have to look up the address for each block of
data, and the moving parts of the drive will have to align in order
to use those blocks. This means that seek, latency, and transfer
time issues will intensify due to the number of times the blocks
must be located in order to read and/or write disk data.