• Provide some service to users on LAN
• Example of services:
  • Access to data
  • Access to shared printers
  • Access to shared pool of modems

 File Server

• Clock speed?
• ??MB RAM
• ??GB Shared hard disk
• Contains network operating system which provides functions such as file access, security, etc.
• Shared peripherals attached
• Requests/data move between server & workstations

• Dedicated file server
  • functions only as file server
  • Recommended approach
• Non-dedicated server
  • functions as a workstation and file server
  • Adv?
  • Disadv?
• Server Consolidation?
• Super Servers
  • Use multiple processors, high-speed disk systems, etc.
  • Ex: HP Proliant
• See Server Farm article
• 64-bit Servers
  • Advantages
    • Surpasses the 4GB memory limit of 32-bit processors
      • Intel Itanium support maximum of 1 petabyte (2 to the 50th power (1,125,899,906,842,624) bytes. 1 petabyte is equal to 1,024 terabytes)
    • Manipulates data and executes instructions in chunks twice as large as a 32-bit processor
  • See HP high-end servers
• Blade Servers
  • Consolidates servers and saves space
  • Not cost effective if replacing just a few servers (as need a chassis for even one blade)
  • See Sun's Blade platform and N1
• Fault Tolerant Servers
  • See NEC's offering
    
• File Server provides 3 basic services (via the Network Operating System)
  • See LAN diagram

• File Services
  • Data and software stored on the File Server's hard disk
  • Users get access to shared data or applications
  • User requests application
    • Copy of program is downloaded to workstation memory
    • REM: Where does processing take place?
  • User requests data file - file is retrieved from the server's hard disk

   

• Security
  • Login Security
    • Username and password security
  • File System Security
    • Access controlled by security services
    • Two issues:
      • What can a user access
      • What can they do to the data
    • Users get rights (permissions) to directories or individual files
    • Examples of Rights
      • Read
      • Write
      • Create

   

• Print Services
  • Print Queues defined (on file server or print server depending on operating system) for printers
  • Print jobs sent from the user's application to the print queue
  • Job is printed in its turn
  • Can cancel print jobs
  • Can change the order of jobs in a print queue

   

 Limitation of File Server for accessing data in a Database Environment

• Fine for Word Processing and Spreadsheet applications
  • How often (when) do these applications need to use the network cable?
• How often (when) does a database application need to use the network cable?
  • Constant access for queries, updates, etc.
• Print a copy of the LAN diagram with no database server for annotation in class
• First let us look at a database application running with just a file server, i.e., no Database server:
  • The DBMS runs on the workstation so must be downloaded from the file server
  • User enters a query:
    • SELECT * FROM CUSTOMER WHERE CITY = "DENVER"
  • File server sends complete Customer file to workstation
  • The workstation processes the query
  • Conclusion: Performance on the network is affected due to extra traffic AND performance for the database application itself could be poor if the workstation is not a powerful machine!

And Now For Something Completely Different (Monty Python)

Database Server

• An example of Client-Server architecture
  • An application is divided into two parts: the Client (front end) and the Server (back end)
  • Abuse of the term!!
• Database Server runs the DBMS engine (kernel) and handles the basic processing, concurrency control, and ensuring data integrity
• LAN with Database Server diagram
• Client machines runs the "tools" of the DBMS
  • Query language, such as SQL
  • Report Writer
• The user requests data from the server via these tools
• User enters the same query, as above, at the Client machine
• The DBMS engine on the Database Server goes through the Customer file and finds which records satisfy the query
• Database Server sends the answer to the client
• Advantage: Performance improved
  • on the network as less traffic &
  • for the query as the Database Server is usually a powerful machine
• Examples of software that supports client-server architecture:
  • SYBASE SQL Server for NetWare
  • Microsoft SQL Server
  • ORACLE
• Most of these systems support multiple Database Servers
  • Example: Database could be spread over mainframe, mini(s), and some Pentium servers

Print Server

• Print jobs sent from workstations to print queues on print server, i.e. jobs spooled to print server (or to print queues on File Server with some operating systems)
• Print server has printer(s) attached
• Job sent to printer when printer is available
• Print Server types:
  • Software Print Server - see LAN with Print Server diagram
    • Microcomputer with print server software installed
    • NetWare
      • run a program called Pserver.exe to make a microcomputer a print server
    • Windows NT/Windows 2000
      • Add and share a printer via the Printers window
      • Makes the computer a Print Server
  • External Hardware Print Server
    • Box with connectors for LAN and parallel connectors for printer
    • See information about the HP JetDirect 510X and the HP JetDirect en3700
  • Internal Hardware Print Server
    • Card that sits in a printer
    • Has parallel port(s) for printers
    • See information about the HP JetDirect 620n (EIO)
    • See information about the HP JetDirect 400n (MIO) in handout
• Hardware Print Servers have better performance than Software Print Servers!

Communication Server

• Dial-out services
  • Allows users to share a pool of modems, or other communication devices, attached to a communication server
  • Advantage:
    • Company does not have to buy a communication device for each user
• Dial-in services
  • Allows users to dial in and get access to network services
  • Compare systems that transfer programs/data to remote users location versus those that take control of a computer on the LAN
• Software: Microsoft Remote Access Service
  • See LAN with Communication Server diagram
  • Be able to draw architecture and explain connectivity options, and speeds supported

 Terminal Servers

• Terminal Services - see diagram
  • Part of Windows 2000 Server or provided as a separate product by a company such as Citrix
  • Read the following articles:
    • Terminal Services
    • Thin Clients
• "Old" Terminal Servers - see diagram
  • Allows terminals (rem: cannot put a NIC in a dumb terminal) to attach to LAN cabling and thereby get access to a host that is attached to the LAN
  • Has multiple ports for dumb terminals and a port to connect to the LAN

Return to Course Notes Page