Compare the update semantics of UNIX when accessing local files with those of NFS and AFS. Under what circumstances might clients become aware of the differences?
What will be an ideal response?
UNIX:strict one-copy update semantics;
NFS:approximation to one-copy update semantics with a delay (~3 seconds) in achieving consistency; AFS:consistency is achieved only on close. Thus concurrent updates at different clients will result in lost updates – the last client to close the file wins.
For a scenario in which the difference between NFS and UNIX update semantics would matter. The difference between AFS and UNIX is much more visible. Lost updates will occur whenever two processes at different clients have a file open for writing concurrently.
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Fill in the blank(s) with the appropriate word(s).