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Selecting LAN server

(Week 3, Monday 9/8/2003)

© Abdou Illia, Fall 2003

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Learning Objective

Explain Server hardware requirement

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Server ?

Workstation A

Workstation B Workstation CServer

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Server Processors

Note: 1. Managing multiple processors requires a lot of work on the part of the NOS2. Doubling the processors might improve computer speed by about 50%

The processor determines computer’s speed Servers can run using one or many processors Number of processors depends on:

NOS to be use Kind of services provided

File and Print services tend to not need multiple processors, but lots of RAM and fast HD

Database service needs fast processors

Slot for Microprocessor(Pentium 4)

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Processors families Intel processors

Celeron Pentium 3 Pentium 4 Pentium 4 Xeon

Intel clones Advanced Micro Devices (AMD) family

K6 series of processors (which compete with Pentium 2 and 3) Athlon series (which compete with Pentium 3 and 4)

Cyrix family

PowerPC family processors used in Apple Macintosh and some UNIX-based servers

Note: 1. Clones are not 100% compatible with Intel’s processors

2. Software vendors usually certify their software against only Intel processors

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Servers and Bus capabilities

At any time a server might be moving megabytes of data (through the bus) to NICs, processors, RAM, disks, etc.

The bus might handle about 5 times data than any single component

The faster the bus, the faster the data transfer

Bus ? All components (NICs, processors, RAM, etc.) are directly or indirectly connected to

the system (mother) board. A component connects to the system board by a data cable, a slot, or a port coming

off the system board In any case, the component always connects to a single bus on the system board The bus is the pathway through all data passes.

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Servers Hard Disks Disk performance depends on

Disk access time measured in milliseconds (ms)(Time for the Read/Write heads to reach data)

Data transfer rate in Mbps Common Data transfer rates: 16.6 Mbps – 1 Gbps Data transfer rate depends on Disk controller, ..

Basically, two types of Disk controllers in use Integrated Device Electronics (IDE) for average transfer rate Small Computer System Interface (SCSI) for higher rateNote: Fibre Channel is a new alternative to SCSI

Server

Disk controller

D V D

Disk drive

SCSI type Data transfer rate

SCSI-1 Up to 5 Mbps

Narrow SCSI-2 Up to 10 Mbps

Wide SCSI-2 Up to 20 Mbps

Ultra SCSI Up to 80 Mbps

SCSI-3 (RISC) Up to 100 Mbps

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Example

Servers Disks capacity Estimation of Hard disk capacity based on calculating space for:

Operating system files User files Application software files General public files Data and database files Server management files

Operating system files Estimated size

Windows 2000 Server 1500 MB

Application software Estimated size

Microsoft Office 150 MB

Microsoft Exchange 150 MB

Accounting software 250 MB

Database Management system 375 MB

User directories Estimated space

Each user 100 MB * 100 10000 MB

Public Directories Estimated size

Word-processing files, spreadsheet files, etc. 650 MB

Server Management software Estimated size

Extra utilities for network management 175 MB

Total 13250 MB

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Disk fault tolerance

Fault tolerance achieved through disk redundancy Disk redundancy can be accomplished:

by installing backup disk by installing RAID (Redundant Array of Independent Disks) drives

RAID’s basic idea is To mirror a disk (i.e. to have a disk and its identical

image) or To spread (or strip) data across many disks

Server’s capability to continue functioning in case of disk failure

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RAID

File

RAID 0 Strips data across multiple disk No redundancy Advantage: Fast data access through multiple reads Disadvantage: Loosing one disk results in loosing data on all disk

RAID 1 Doesn’t strip data across many disk Mirrors data between two disks Data kept synchronized between two disks Advantage: Fault-tolerance, i.e. If one disk fails, the other continue working until failed disk can be

replaced Disadvantage: Only half of available storage space is used.

File

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RAID

RAID 3 Spreads data across multiple disks and uses ECC bits for recovery purpose in case of problem ECC bits determined based on data stored on data disks If one data disk fails, disk controller automatically regenerates missing data

Data spread across these disks

Last disk contains ECC* data for

disks 1-4

* Error Checking and Correcting

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Summary Questions1) T or F: All servers benefit from having multiple

processors.

2) In a server, what does a Bus do?a. Convert bits into signalsb. Act as the central transfer mechanism for all datac. Update the motherboard

3) Generally speaking, how much improvement in server processor performance does doubling the number of processors in a server gain?

a. 25%b. 50%c. 100%

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Summary Questions

4) What are the two major competitors of Intel in processor market?

5) T or F: IDE Disk controllers offer higher transfer rate than SCSI Disk controllers.

6) Compare the following RAID levels: RAID 0, RAID 1 and RAID 3