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STORAGE ARCHITECTURE/ GETTING STARTED: SAN SCHOOL 101

Join Marc Farley, President of Building Storage, Inc. as he covers the basics of storage area networks (SANs), I/O path, storage subsystems, RAID, SAN network technology, file systems, and more.

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STORAGE ARCHITECTURE/ GETTING STARTED: SAN SCHOOL 101

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  1. STORAGE ARCHITECTURE/GETTING STARTED:SAN SCHOOL 101 Marc Farley President of Building Storage, Inc Author, Building Storage Networks, Inc.

  2. Agenda • Lesson 1: Basics of SANs • Lesson 2: The I/O path • Lesson 3: Storage subsystems • Lesson 4: RAID, volume management and virtualization • Lesson 5: SAN network technology • Lesson 6: File systems

  3. Lesson #1 Basics of storage networking

  4. Connecting

  5. Connecting • Networking or bus technology • Cables + connectors • System adapters + network device drivers • Network devices such as hubs, switches, routers • Virtual networking • Flow control • Network security

  6. Storing

  7. Storing • Device (target) command and control • Drives, subsystems, device emulation • Block storage address space manipulation (partition management) • Mirroring • RAID • Striping • Virtualization • Concatentation

  8. Filing

  9. Filing • Namespace presents data to end users and applications as files and directories (folders) • Manages use of storage address spaces • Metadata for identifying data • file name • owner • dates

  10. Connecting, storing and filing as a complete storage system Connecting

  11. NAS and SAN analysis NAS is filing over a network SAN is storing over a network NAS and SAN are independent technologies They can be implemented independently They can co-exist in the same environment They can both operate and provide services to the same users/applications

  12. Protocol analysis for NASand SAN Filing NAS SAN Network Storing Connecting

  13. Integrated SAN/NAS environment NAS Server+SAN Initiator “NAS Head” Filing Storing Connecting Connecting

  14. Common wiring with NASand SAN NAS Head Filing Storing Connecting

  15. Lesson #2 The I/O path

  16. Host hardware path components MemoryBus System I/O Bus Storage Adapter (HBA) Memory Processor

  17. Host software path components Application Multi-Pathing VolumeManager Device Driver Filing System CacheManager Operating System

  18. Network hardware path components Switches, hubs, routers, bridges, gatways Port buffers, processors Backplane, bus, crossbar, mesh, memory Cabling Fiber optic Copper

  19. Network software path components Access and Security Virtual Networking FlowControl Fabric Services Routing

  20. Subsystem path components Access and Security NetworkPorts Cache Resource Manager Internal Busor Network

  21. Device and media path components Disk drives Tape drives Tape Media Solid state devices

  22. The end to end I/O path picture Storage Adapter (HBA) Device Driver CacheManager System I/O Bus MemoryBus VolumeManager Memory Filing System Multi-Pathing Operating System App Processor Virtual Networking FlowControl Access and Security Fabric Services Routing Network Systems Cabling SubsystemNetwork Poirt Access and Security Disk drives Tape drives Resource Manager Internal Busor Network Cache

  23. Storage subsystems Lesson #3

  24. Generic storage subsystem model Controller (logic+processors)Access control Resource manager Storage Resources NetworkPorts Internal Bus or Network Cache Memory Power

  25. Redundancy for high availability • Multiple hot swappable power supplies • Hot swappable cooling fans • Data redundancy via RAID • Multi-path support • Network ports to storage resources

  26. Exportedstorage Exportedstorage Physicalstorage device Physicalstorage device Exportedstorage Exportedstorage Physicalstorage device Physicalstorage device Exportedstorage Exportedstorage Exportedstorage Exportedstorage Physical and virtual storage Subsystem Controller Resource Manager (RAID, mirroring, etc.) HotSpare Device

  27. SCSI communications architectures determine SAN operations • SCSI communications are independent of connectivity • SCSI initiators (HBAs) generate I/O activity • They communicate with targets • Targets have communications addresses • Targets can have many storage resources • Each resource is a single SCSI logical unit (LU) with a universal unique ID (UUID) - sometimes referred to as a serial number • An LU can be represented by multiple logical unit numbers (LUNs) • Provisioning associates LUNs with LUs & subsystem ports • A storage resource is not a LUN, it’s an LU

  28. SCSI LU UUID B SCSI LU UUID A SCSI LU UUID C SCSI LU UUID D Physicalstorage devices Physicalstorage devices Physicalstorage devices Provisioning storage LUN 0 LUN 1 Port S1 LUN 1 LUN 2 Port S2 LUN 2 Port S3 LUN 3 LUN 3 Port S4 LUN 0 Controller functions

  29. SCSI LU UUID A Path 1 Path 2 Multipathing LUN X MP SW LUN X

  30. ExportedVolume ExportedVolume Controller Cache Manager ExportedVolume ExportedVolume Caching Write Caches 1. Write Through (to disk) 2. Write Back (from cache) Read Caches 1. Recently Used 2. Read Ahead

  31. Tape subsystems TapeDrive TapeDrive Tape Subsystem Controller TapeDrive TapeDrive Robot Tape Slots

  32. Subsystem management Now with SMIS Management station browser-based network mgmt software Ethernet/TCP/IP Out-of-band management port In-band management ExportedStorage Resource Storage Subsystem

  33. Data redundancy 2n n+1 Duplication Parity Difference -1 d(x) = f(x) – f(x-1) f(x-1)

  34. Duplication redundancy with mirroring Host-based Within a subsystem I/O PathA MirroringOperator I/O Path I/O PathB Terminate I/O & regenerate new I/Os Error recovery/notification

  35. Duplication redundancy with remote copy Host Uni-directional (writes only) A A B A A

  36. Point-in-time snapshot Subsystem Snapshot Host A A B A A C

  37. Lesson #4 RAID, volume managementand virtualization

  38. RAID = parity redundancy 2n Duplication Parity Difference n+1 -1 d(x) = f(x) – f(x-1) f(x-1)

  39. History of RAID • Late 1980s R&D project at UC Berkeley • David Patterson • Garth Gibson (independent) • Redundant array of inexpensive disks • Striping without redundancy was not defined (RAID 0) • Original goals were to reduce the cost and increase the capacity of large disk storage

  40. Benefits of RAID • Capacity scaling • Combine multiple address spaces as a single virtual address • Performance through parallelism • Spread I/Os over multiple disk spindles • Reliability/availability with redundancy • Disk mirroring (striping to 2 disks) • Parity RAID (striping to more than 2 disks)

  41. ExportedRAIDdisk volume (1 address) Capacity scaling Storage extent 1 Storage extent 2 Storage extent 3 Storage extent 4 Combined extents 1 - 12 Storage extent 5 Storage extent 6 Storage extent 7 Storage extent 8 Storage extent 9 Storage extent10 Storage extent11 Storage extent12 RAID Controller(resourcemanager)

  42. 1 6 5 2 3 4 Performance RAID controller (microsecond performance) Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive Disk drives (Millisecond performance)from rotational latency and seek time

  43. Parity redundancy • RAID arrays use XOR for calculating parityOperand 1 Operand 2 XOR Result False False False False True True True False True True True False • XOR is the inverse of itself • Apply XOR in the table above from right to left • Apply XOR to any two columns to get the third

  44. Reduced mode operations • When a member is missing, data that is accessed must be reconstructed with xor • An array that is reconstructing data is said to be operating in reduced mode • System performance during reduced mode operations can be significantly reduced XOR {M1&M2&M3&P}

  45. Parity rebuild RAID Parity Rebuild • The process of recreating data on a replacement member is called a parity rebuild • Parity rebuilds are often scheduled for non-production hours because performance disruptions can be so severe XOR {M1&M2&M3&P}

  46. RAID 0+1, 10 Hybrid RAID: 0+1 RAID Controller Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive Diskdrive 1 2 3 5 4 Mirrored pairs of striped members

  47. Volume management and virtualization • Storing level functions • Provide RAID-like functionality in host systems and SAN network systems • Aggregation of storage resources for: • scalability • availability • cost / efficiency • manageability

  48. OS kernel File system Volume management • RAID & partition management • Device driver layer between the kernel and storage I/O drivers Volume Manager Volume Manager HBA drivers HBAs

  49. Volume manager Server system Volume managers can use all available connections and resources and can span multiple SANs as well as SCSI and SAN resources Virtual Storage SCSI disk resource SCSI HBA SCSI Bus SAN disk resources HBA drivers SAN cable SAN Switch SAN HBA

  50. SAN storage virtualization • RAID and partition management in SAN systems • Two architectures: • In-band virtualization (synchronous) • Out-of-band virtualization (asynchronous)

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