Some systems provide file sharing by maintaining a single copy of a file. Other systems maintain several copies, one for each of the users sharing the file. Discuss the relative merits of each approach.

Explanation:

When you have a single copy, a large number of concurrent updates that are supposed to go to a file may result in the user obtaining incorrect information. This incorrect information obtained them leads to the file being left in an incorrect state. When you have a lot of or multiple copies, then storage waste exist and the various copies might happen not to be consistent with respect one other. In summary, what happens is that

a) Using one copy saves space, but also the change might have an effect on all the users.

b) Using multiple copies avoids eliminates the change problem, while creating its own problems, using more space.