Lecture 6: Storage Devices, Metrics, RAID, I/O Benchmarks, and BussesMotivation: Who Cares About I/O?Storage System IssuesI/O SystemsTechnology TrendsStorage Technology DriversHistorical PerspectiveDisk HistorySlide 9Slide 10MBits per square inch: DRAM as % of Disk over timeAlternative Data Storage Technologies: Early 1990sDevices: Magnetic DisksDisk Device TerminologyAdvantages of Small Form-factor Disk DrivesTape vs. DiskCurrent Drawbacks to TapeAutomated Cartridge SystemRelative Cost of Storage Technology—Late 1995/Early 1996OutlineDisk I/O PerformanceResponse Time vs. ProductivityResponse Time & ProductivityDisk Time ExampleSlide 25Processor Interface IssuesI/O InterfaceMemory Mapped I/OProgrammed I/O (Polling)Interrupt Driven Data TransferDirect Memory AccessInput/Output ProcessorsRelationship to Processor ArchitectureSlide 34SummarySummary: Relationship to Processor ArchitectureSlide 37Network Attached StorageManufacturing Advantages of Disk ArraysReplace Small # of Large Disks with Large # of Small Disks! (1988 Disks)Array ReliabilityRedundant Arrays of DisksRedundant Arrays of Disks RAID 1: Disk Mirroring/ShadowingRedundant Arrays of Disks RAID 3: Parity DiskRedundant Arrays of Disks RAID 5+: High I/O Rate ParityProblems of Disk Arrays: Small WritesSubsystem OrganizationSystem Availability: Orthogonal RAIDsSystem-Level AvailabilitySummary: Redundant Arrays of Disks (RAID) TechniquesSlide 51ABCs of UNIX File SystemsSlide 53Slide 54Typical File Server ArchitectureAUSPEX NS5000 File ServerBerkeley RAID-II Disk Array File ServerI/O BenchmarksSlide 59I/O Benchmarks: Transaction ProcessingSlide 61I/O Benchmarks: TP by Anon et. alI/O Benchmarks: TP1 by Anon et. alSlide 64I/O Benchmarks: Old TPC BenchmarksI/O Benchmarks: TPC-C Complex OLTPI/O Benchmarks: TPC-D Complex Decision Support WorkloadI/O Benchmarks: TPC-W Transactional Web BenchmarkTPC-C Performance tpm(c)TPC-C Price/Performance $/tpm(c)TPC-D Performance/Price 300 GBTPC-D Performance 1TBSPEC SFS/LADDIS Predecessor: NFSstonesSPEC SFS/LADDISExample SPEC SFS Result: DEC AlphaWillyExample Willy: DS 5000Sprite's Log Structured File SystemWilly: DS 5000 Number Bytes TouchedSummary: I/O BenchmarksSlide 81Interconnect TrendsBackplane ArchitecturesBus-Based InterconnectSlide 85Bus ProtocolsSynchronous Bus ProtocolsAsynchronous HandshakeRead TransactionBus ArbitrationBus OptionsSCSI: Small Computer System Interface1993 I/O Bus Survey (P&H, 2nd Ed)1993 MP Server Memory Bus SurveyNext TimeFTC.W99 1Lecture 6: Storage Devices, Metrics, RAID, I/O Benchmarks, and BussesProf. Fred ChongECS 250A Computer ArchitectureWinter 1999(Adapted from Patterson CS252 Copyright 1998 UCB)FTC.W99 2Motivation: Who Cares About I/O?•CPU Performance: 60% per year•I/O system performance limited by mechanical delays (disk I/O)< 10% per year (IO per sec or MB per sec)•Amdahl's Law: system speed-up limited by the slowest part!10% IO & 10x CPU => 5x Performance (lose 50%)10% IO & 100x CPU => 10x Performance (lose 90%)• I/O bottleneck: Diminishing fraction of time in CPUDiminishing value of faster CPUsFTC.W99 3Storage System Issues•Historical Context of Storage I/O•Secondary and Tertiary Storage Devices•Storage I/O Performance Measures•Processor Interface Issues•Redundant Arrays of Inexpensive Disks (RAID)•ABCs of UNIX File Systems•I/O Benchmarks•Comparing UNIX File System Performance•I/O BussesFTC.W99 4I/O SystemsProcessorCacheMemory - I/O BusMainMemoryI/OControllerDisk DiskI/OControllerI/OControllerGraphicsNetworkinterruptsinterruptsFTC.W99 5Technology TrendsDisk Capacity now doubles every 18 months; before1990 every 36 months• Today: Processing Power Doubles Every 18 months• Today: Memory Size Doubles Every 18 months(4X/3yr)• Today: Disk Capacity Doubles Every 18 months• Disk Positioning Rate (Seek + Rotate) Doubles Every Ten Years!The I/OGAPThe I/OGAPFTC.W99 6Storage Technology Drivers•Driven by the prevailing computing paradigm–1950s: migration from batch to on-line processing–1990s: migration to ubiquitous computing»computers in phones, books, cars, video cameras, …»nationwide fiber optical network with wireless tails•Effects on storage industry:–Embedded storage»smaller, cheaper, more reliable, lower power–Data utilities»high capacity, hierarchically managed storageFTC.W99 7Historical Perspective•1956 IBM Ramac — early 1970s Winchester–Developed for mainframe computers, proprietary interfaces–Steady shrink in form factor: 27 in. to 14 in.•1970s developments–5.25 inch floppy disk form factor –early emergence of industry standard disk interfaces»ST506, SASI, SMD, ESDI•Early 1980s–PCs and first generation workstations•Mid 1980s–Client/server computing –Centralized storage on file server»accelerates disk downsizing: 8 inch to 5.25 inch–Mass market disk drives become a reality»industry standards: SCSI, IPI, IDE»5.25 inch drives for standalone PCs, End of proprietary interfacesFTC.W99 8Disk HistoryData densityMbit/sq. in.Capacity ofUnit ShownMegabytes1973:1. 7 Mbit/sq. in140 MBytes1979:7. 7 Mbit/sq. in2,300 MBytessource: New York Times, 2/23/98, page C3, “Makers of disk drives crowd even more data into even smaller spaces”FTC.W99 9Historical Perspective•Late 1980s/Early 1990s:–Laptops, notebooks, (palmtops)–3.5 inch, 2.5 inch, (1.8 inch form factors)–Form factor plus capacity drives market, not so much performance»Recently Bandwidth improving at 40%/ year–Challenged by DRAM, flash RAM in PCMCIA cards»still expensive, Intel promises but doesn’t deliver»unattractive MBytes per cubic inch–Optical disk fails on performance (e.g., NEXT) but finds niche (CD ROM)FTC.W99 10Disk History1989:63 Mbit/sq. in60,000 MBytes1997:1450 Mbit/sq. in2300 MBytessource: New York Times, 2/23/98, page C3, “Makers of disk drives crowd even mroe data into even smaller spaces”1997:3090 Mbit/sq. in8100 MBytesFTC.W99 11MBits per square inch: DRAM as % of Disk over time0%5%10%15%20%25%30%35%40%45%1974 1980 1986 1992 1998source: New York Times, 2/23/98, page C3, “Makers of disk drives crowd even mroe data into even smaller spaces”470 v. 3000 Mb/si9 v. 22 Mb/si0.2 v. 1.7 Mb/siFTC.W99 12Alternative Data Storage Technologies: Early 1990sCap BPI TPI BPI*TPI Data Xfer AccessTechnology (MB) (Million) (KByte/s) TimeConventional Tape:Cartridge (.25") 150 12000 104 1.2 92 minutesIBM 3490 (.5") 800 22860 38 0.9 3000 secondsHelical Scan Tape:Video (8mm) 4600 43200