File Services

File Services

File services enable networked computers to share files. This capability was one of the primary reasons networking personal computers initially came about. File services include all network functions centering on the storage, retrieval, or movement of data files. A common feature of file services is access control and transaction logging. File services enable users to read, write, and manage files and data, but they also should restrict users to authorized file operations so that files aren’t accidentally overwritten or deleted. In addition, file services should track unauthorized actions.

File services are an important part of server-based and peer to-peer networks. Two types of servers exist: dedicated and non-dedicated. Dedicated servers do nothing but fulfill requests to network clients. These are commonly found in client-server environments. Non-dedicated servers do double duty by requesting and providing services, and they are the backbone of the peer-to-peer structure. (A Windows 95 machine used to access files on the network and to provide access to a shared printer is an example of a non-dedicated server.)

Dedicated file servers have the following benefits:

Files are in a specific place where they can be reliably archived.
Central file servers can be managed more efficiently, with user and security data located in a single database.
Central file servers can contain expensive, high-performance hardware that expedites file services and makes the file servers more reliable.
The cost of specialized file server technology is shared by a large number of users.
Centralized networks are more scaleable.

The following drawbacks, however, should be considered with regard to centralized file services:

When all data is stored on a single server, a single point of failure exists. If the server fails, all data becomes unavailable, making proper design, management, and backup of the server essential.
Because all clients contend for file services from a single source, average file-access times might be slower with a centralized file server than when files are stored on individual, local hard drives.

Centralized file services generally are chosen for organizations that want to achieve the highest levels of protection for their data files.

Take care when discussing the words “centralized” and “distributed.” These terms describe the utilization method of processor resources, file resources, or administrative tasks. For instance, a single administrator can watch over a network with a single file server and many PC clients. This network utilizes centralized administration and provides for centralized file access, but because the clients do their own processing, the network itself fits under the distributed computing model.

In a peer-to-peer network environment, any computer can share its files and applications with any other computer. The sharing of services must be established for each individual computer, and each user must have the skills required to manage the networking services on her PC. Because services are provided by many different computers, users must become aware of which computers are providing which services. Clearly, the skills and responsibility required of users are greater than for centralized file services.

Some advantages of distributed file storage include the following:

No single point of failure exists. When a computer fails, only the files stored on that computer become unavailable.
Individuals typically experience faster access for files located on local hard drives than for files on centralized file servers.
No specialized server hardware is required. File services can be provided with standard PCs.

Some negative issues related to distributed file storage include the following:

It’s more difficult to manage the file service and to protect the integrity of files. File backup is more difficult when files are distributed across many PCs.
Individual PCs generally don’t have high-reliability hardware, such as uninterruptible power supplies and disk mirroring.
File services provided by peers typically are not as fast or as flexible as file services provided by a central file server that is specifically designed for the purpose.
Instead of upgrading one central file server when higher performance is required, you must upgrade each computer.

Organizations tend to choose peer-to-peer networking for two primary reasons. One is a desire to network with their current stock of PCs without the expense of a centralized server. Another is that peer-to-peer is an informal networking approach that fits the working style of many organizations. Microsoft implements peer-to-peer networking components into Windows for Workgroups, Windows 95, and Windows NT Workstation. Any of these operating systems is capable of sharing and accessing network resources without the aid of a centralized server. These systems are not optimized for file and printer sharing, however, and this sort of network structure is only recommended for smaller networks with limited security concerns.

Some key file services include:

File transfer
File storage
Data migration
File archiving
File-update synchronization

Each of these services is discussed in the following sections.

Further Information