Thomas Kunz
Systems and Computer Engineering
8
File Systems: Consistency Problems
nTHE big problem of distributed, loosely coupled
systems
–are all
views on data the same?
–how and
when should changes be propagated to what users?
nWeak consistency
–many
algorithms offering strong consistency (e.g., via atomic updates) cannot be used in mobile environments
–invalidation
of data located in caches through a server is very problematic if the mobile computer is currently not
connected to the
network
–occasional
inconsistencies have to be tolerated, but conflict resolution strategies must be applied afterwards to
reach consistency again
nConflict detection
–content
independent: version numbering, time-stamps
–content
dependent: dependency graphs