Selecting LAN serverLearning ObjectiveServer ?Server ProcessorsProcessors familiesServers and Bus capabilitiesServers Hard DisksServers Disks capacityDisk fault toleranceRAIDSlide 11Summary QuestionsSlide 131Selecting LAN server(Week 3, Monday 9/8/2003)© Abdou Illia, Fall 20032Learning ObjectiveExplain Server hardware requirement3Server ?Workstation AWorkstation BWorkstation CServer4Server 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: 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 processorsSlot for Microprocessor(Pentium 4)5Processors 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 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 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.7Servers 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 SCSISCSI type Data transfer rateSCSI-1 Up to 5 MbpsNarrow SCSI-2 Up to 10 MbpsWide SCSI-2 Up to 20 MbpsUltra SCSI Up to 80 MbpsSCSI-3 (RISC) Up to 100 Mbps8ExampleServers 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 filesOperating system files Estimated sizeWindows 2000 Server 1500 MBApplication software Estimated sizeMicrosoft Office 150 MBMicrosoft Exchange 150 MBAccounting software 250 MBDatabase Management system 375 MBUser directories Estimated spaceEach user 100 MB * 100 10000 MBPublic Directories Estimated sizeWord-processing files, spreadsheet files, etc. 650 MBServer Management software Estimated sizeExtra utilities for network management 175 MBTotal 13250 MB9Disk 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 disksServer’s capability to continue functioning in case of disk failure10RAIDRAID 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%13Summary 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