6.2.2. Where Users Access Shared Data

When sharing data among users, it is a common practice to have a central server (or group of servers) that make certain directories available to other machines on the network. This way data is stored in one place; synchronizing data between multiple machines is not necessary.
Before taking this approach, you must first determine what systems are to access the centrally-stored data. As you do this, take note of the operating systems used by the systems. This information has a bearing on your ability to implement such an approach, as your storage server must be capable of serving its data to each of the operating systems in use at your organization.
Unfortunately, once data is shared between multiple computers on a network, the potential for conflicts in file ownership can arise.

6.2.2.1. Global Ownership Issues

There are benefits if data is stored centrally and is accessed by multiple computers over a network. However, assume for a moment that each of those computers has a locally-maintained list of user accounts. What if the list of users on each of these systems are not consistent with the list of users on the central server? Even worse, what if the list of users on each of these systems are not even consistent with each other?
Much of this depends on how users and access permissions are implemented on each system, but in some cases it is possible that user A on one system may actually be known as user B on another system. This becomes a real problem when data is shared between these systems, as data that user A is allowed to access from one system can also be read by user B from another system.
For this reason, many organizations use some sort of central user database. This assures that there are no overlaps between user lists on different systems.