There are places I'll remember all my life, though some have changed.
—From the song In My Life by the Beatles
Stored data must be remembered perfectly. Many computer technologies have been invented in an attempt to achieve perfect data recall in the presence of electronic, mechanical, and human errors. RAID disk technologies, tape backup systems, error correcting memory, remote data replication, and other techniques are used today to ensure that when data is written it can be quickly and reliably retrieved even after much time has elapsed, perhaps years.
There are numerous commercially developed and community-developed disk file systems; Wikipedia lists almost 100 at http://en.wikipedia.org/wiki/Comparison_of_file_systems ...