1. 1 Selecting LAN server (Week 3, Monday 9/8/2003) © Abdou Illia, Fall 2003

2. 2 Learning Objective Explain Server hardware requirement

3. 3 Server ? Workstation A Workstation B Workstation C Server

4. 4 Server Processors Note: 1. Managing multiple processors requires a lot of work on the part of the NOS 2. 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)

5. 5 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

6. 6 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.

7. 7 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 rate Note: Fibre Channel is a new alternative to SCSI SCSI typeData transfer rate SCSI-1Up to 5 Mbps Narrow SCSI-2Up to 10 Mbps Wide SCSI-2Up to 20 Mbps Ultra SCSIUp to 80 Mbps SCSI-3 (RISC)Up to 100 Mbps

8. 8 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 filesEstimated size Windows 2000 Server1500 MB Application softwareEstimated size Microsoft Office150 MB Microsoft Exchange150 MB Accounting software250 MB Database Management system375 MB User directoriesEstimated space Each user 100 MB * 10010000 MB Public DirectoriesEstimated size Word-processing files, spreadsheet files, etc.650 MB Server Management softwareEstimated size Extra utilities for network management175 MB Total13250 MB

9. 9 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

10. 10 RAID 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.

11. 11 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

12. 12 Summary Questions 1)T or F: All servers benefit from having multiple processors. 2)In a server, what does a Bus do? a. Convert bits into signals b. Act as the central transfer mechanism for all data c. 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%

13. 13 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