Re: Terminology for replication

[tytso at mit.edu]

Jacob,

	Different communities of interest use different terminology, and
so context is very important.  

	For example, ftp maintainers use "mirroring" to refer to
periodic copying (usually every 24 hours) of a master repository of
files to subsidary locations.  There usually isn't any coordination (or
at least very little coordination) between the master repository sites
and the ftp mirror sites.  In the case of RAID disks, however, there are
stronger guarantees between what is stored on the various mirrored
disks.

	In the case of "caching", there are some caches where there are
no 100% safe methods against outdated objects in the cache, as per your
proposed definition.  However, if you are talking about memory
internal/external L1/L2 caches in modern computer systems, there are
carefully designed cache consistency mechanisms to make sure that the
caches get updated when necessary.

       So it all depends on the context of how you are using the words.
It is certainly a good thing to try to make sure everybody is using
certain words in the same way when discussing a particular topic or in a
particular specification.  I very much doubt that we could standardize a
set of meanings across the entire wider community, though.

						   - Ted