4. LAN Servers
Servers
- 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
- File Server provides 3 basic services (via
the Network Operating System)
- 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
- 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
- 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
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:
- "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
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