11Selecting LAN server(Week 3, Monday 9/8/2003)© Abdou Illia, Fall 20032Learning Objective Explain Server hardware requirement3Server ?Workstation AWorkstation BWorkstation CServer24Server ProcessorsNote: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:Î NOS to be useÎ Kind of services providedÎ File and Print services tend to not need multiple processors, but lots of RAM and fast HDÎ Database service needs fast processorsSlot for Microprocessor(Pentium 4)5Processors families Intel processorsÎ CeleronÎ Pentium 3Î Pentium 4Î 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 serversNote:1. Clones are not 100% compatible with Intel’s processors2. Software vendors usually certify their software against only Intel processors6Servers 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 transferBus ? All components (NICs, processors, RAM, etc.) are directly or indirectly connected tothe 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.37Servers Hard Disks Disk performance depends onÎDisk access time measured in milliseconds (ms)(Time for the Read/Write heads to reach data)ÎData transfer rate in MbpsÎ Common Data transfer rates: 16.6 Mbps – 1 GbpsÎ Data transfer rate depends on Disk controller, ..Basically, two types of Disk controllers in useÎ Integrated Device Electronics (IDE) for average transfer rateÎ Small Computer System Interface (SCSI) for higher rateNote:Fibre Channel is a new alternative to SCSIUp to 100 MbpsSCSI-3 (RISC)Up to 80 MbpsUltra SCSIUp to 20 MbpsWide SCSI-2Up to 10 MbpsNarrow SCSI-2Up to 5 MbpsSCSI-1Data transfer rateSCSI type8ExampleServers Disks capacity Estimation of Hard disk capacity based on calculating space for:Î Operating system files Î User filesÎ Application software files Î General public filesÎ Data and database files Î Server management filesEstimated spaceUser directories10000 MBEach user 100 MB * 100175 MBExtra utilities for network managementEstimated sizeServer Management software650 MBWord-processing files, spreadsheet files, etc.250 MBAccounting software150 MBMicrosoft Exchange150 MBMicrosoft Office13250 MBTotalEstimated sizePublic Directories375 MBDatabase Management systemEstimated sizeApplication software1500 MBWindows 2000 ServerEstimated sizeOperating system files9Disk fault tolerance Fault tolerance achieved through disk redundancy  Disk redundancy can be accomplished:Î by installing backup diskÎ 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 disksServer’s capability to continue functioning in case of disk failure410RAIDRAID 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 diskRAID 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.11RAIDRAID 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 dataData spread across these disksLast disk contains ECC* data for disks 1-4* Error Checking and Correcting12Summary 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 motherboard3) 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%513Summary Questions4) 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