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Disk Storage Systems

Disk Storage Systems. Module 2.5. Disk Storage Systems. After completing this module, you will be able to: Describe the components of an intelligent storage system Describe the configuration of a logical disk Discuss the methods employed to ensure that a host can access a storage volume

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Disk Storage Systems

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  1. Disk Storage Systems Module 2.5

  2. Disk Storage Systems After completing this module, you will be able to: • Describe the components of an intelligent storage system • Describe the configuration of a logical disk • Discuss the methods employed to ensure that a host can access a storage volume • Discuss back end volume protection • Discuss front end host configuration • Describe the I/O flow from the back end to the physical disks Disk Storage Systems

  3. Lesson: Intelligent Storage System Overview After completing this lesson, you will be able to: • List the benefits of intelligent storage systems • Compare and contrast integrated and modular approaches to intelligent storage systems • Describe the I/O flow through the storage system • Describe the logical elements of an intelligent storage system Disk Storage Systems

  4. What is an Intelligent Storage System? • A disk storage system which distributes data over several devices and manages access to that data. • When implemented properly, it provides the following benefits over individual storage devices: • Increased capacity • Improved performance • Easier data management • Better data availability • More robust backup/restore capabilities • Improved flexibility and scalability Disk Storage Systems

  5. Monolithic (Integrated) Storage Systems FC Ports Port Processors Monolithic Cache RAID Controllers Disk Storage Systems

  6. Modular Storage Systems Modular Rack Host Interface Host Interface Servers Cache Cache FC Switches RAID RAID Controller A Controller B Disk Modules Control Modulewith Disks Disk Storage Systems

  7. Cache Elements in an Intelligent Storage System Intelligent Storage System Front End Back End Physical Disks Cache Host Connectivity Disk Storage Systems

  8. Intelligent Storage System: Front End Intelligent Storage System Front End Back End Physical Disks Cache Host Connectivity Ports Controllers Note: Include redundancy in the channels to and from the ports. Disk Storage Systems

  9. Request 1 FRONT END Request 2 4 2 3 1 Request 3 Request 4 Front End Command Queuing Without Command Queuing Request 1 FRONT END Request 2 2 4 3 2 1 1 Request 3 3 Request 4 4 With Command Queuing 2 1 3 4 Disk Storage Systems

  10. Intelligent Storage System: Cache Intelligent Storage System Front End Back End Physical Disks Cache Host Connectivity Disk Storage Systems

  11. Intelligent Storage System: Back End Intelligent Storage System Front End Back End Physical Disks Cache Host Connectivity Controllers Ports Disk Storage Systems

  12. Intelligent Storage System: Physical Disks Intelligent Storage System Front End Back End Physical Disks Cache Host Connectivity Disk Storage Systems

  13. I/O Example: Read Requests I/O Example: Read Requests Intelligent Storage System Front End Back End Physical Disks Cache Host Connectivity Disk Storage Systems

  14. I/O Example: Write Requests Intelligent Storage System Front End Back End Physical Disks Cache Host Connectivity Disk Storage Systems

  15. LUN 0 LUN 1 LUN 2 What the Host Sees Intelligent Storage System Host Physical Disks Back End Cache Host LUN 0 LUN 1 LUN 2 Disk Storage Systems

  16. LUN 0 LUN 1 LUN 2 The Host and Logical Device Names Intelligent Storage System Host VolumeManager Physical Disks Back End /dev/rdsk/c1t1d0 /dev/rdsk/c1t1d1 Cache Host VolumeManager LUN 0 LUN 1 LUN 2 \\.\PhysicalDrive0 Disk Storage Systems

  17. LUN 1 Disk Organization in a Storage System Intelligent Storage System Host Back End Physical Disks LUN 0 LUN 0 Cache LUN 1 Host Disk Storage Systems

  18. Lesson Summary Key points covered in this lesson: • An intelligent disk storage system: • Distributes data over several devices and manages access to that data • Has a front end, cache, a back end, and physical disks. • Use the virtual disks to provide optimal performance and capacity. • Individual disks within a RAID set can be divided into logical units. • The same concept can be applied to entire RAID sets. Disk Storage Systems

  19. Lesson: Cache – A Closer Look After completing this lesson, you will be able to: • Define cache • Distinguish between multipurpose cache and configurable cache • Describe cache hits and misses • Describe algorithms to manage cache • Trace the I/O flow from the cache to the back end to the physical disks Disk Storage Systems

  20. What is Cache in a Storage System A memory space used by a disk storage system to reduce the time required to read data/write data. It is usually made from very fast memory Cache ReadRequest WriteRequest Acknowledgment Disk Storage Systems

  21. How Cache is Structured Data Store Tag RAM Disk Storage Systems

  22. Read Cache ‘Hits’ and ‘Misses’ Data found in cache = ‘Hit’ Cache ReadRequest No data found = ‘Miss’ Cache ReadRequest Disk Storage Systems

  23. Algorithms Used to Manage Read Cache • Least Recently Used (LRU) • Determines which items areaccessed frequently/infrequently • Discards least recently used data • Read Ahead (pre-fetch) • Accesses data sequentially and putsit into cache before it is requested • May assume that data recently accessed will not be needed again. New Data Oldest Data Disk Storage Systems

  24. Write Algorithms Write-through Cache Cache WriteRequest Acknowledgement Write-back Cache WriteRequest Acknowledgement Disk Storage Systems

  25. Write Cache: Performance • Manage peak I/O requests “bursts” through flushing • Least-recently used pages are flushed from cache to the drives • For maximum performance: • Provide headroom in write cache for I/O bursts • Coalesce small host writes into larger disk writes • Improve sequentiality at the disk Disk Storage Systems

  26. Lesson Summary Key points covered in this lesson: • Cache is a memory space used by a disk storage system to reduce the time required to read data/write data. • It can speed up both read and write operations. • Cache read algorithms include: • Least Recently Used (LRU) • Read Ahead (pre-fetch) • Cache write algorithms include: • Write-through • Write-back Disk Storage Systems

  27. Module Summary Key points covered in this module: • An intelligent disk storage system distributes data over several devices and manages access to that data. • Monolithic storage systems are generally aimed at the enterprise level, centralizing data in a powerful system with hundreds of drives. • Modular storage systems provide storage to a smaller number of (typically) Windows or Unix servers than larger integrated storage systems. • Cache is an important part of intelligent disk storage systems as it can be used to improve performance. Disk Storage Systems

  28. Check Your Knowledge • What are the parts of an Intelligent Disk Subsystem? • What is the difference between a monolithic and a modular array? • What is the difference between cache hit and a cache miss? • What is the difference between Least Recently Used and Read Ahead cache? • What is the difference between Write-through and Write-back cache? Disk Storage Systems

  29. Apply Your Knowledge Upon completion of this case study, you will be able to: • Describe the basic architecture of the CLARiiON modular storage array. • Describe the basic architecture of the Symmetrix integrated storage array. Disk Storage Systems

  30. CLARiiON CX3-80 Architecture 1/2/4 Gb/s Fibre Channel Front End UltraScale Storage Processor UltraScale Storage Processor CLARiiON Messaging Interface (CMI) Multi-Lane PCI-Express bridge link Fibre Channel Fibre Channel SPS Power supply Mirrored cache Mirrored cache Fan Fan Fan Fan CPU CPU CPU CPU SPS Power supply FC FC FC FC FC FC FC FC 4Gb/s LCC 4Gb/s LCC 2/4 Gb/s Fibre Channel Back End 2/4 Gb/s Fibre Channel Back End 4Gb/s LCC 4Gb/s LCC 4Gb/s LCC 4Gb/s LCC 4Gb/s LCC 4Gb/s LCC Up to 480 drives max per storage system (CX3-80) Disk Storage Systems

  31. Assigning CLARiiON LUNs to Hosts • CLARiiON disks are grouped into RAID Groups • Disks from any enclosure may be used in a RAID Group • All disks in a RAID Group must be either Fibre Channel or ATA • A RAID Group is the ‘RAID set’ discussed earlier • A RAID Group may be a single disk, or RAID Level 0, 1, 1/0, 3 or 5 • The RAID Group is then partitioned into LUNs • All LUNs in a RAID Group will be the same RAID Level • The LUNs are then made accessible to hosts • CLARiiON-resident software ensures that LUNs are seen only by the hosts that own them Disk Storage Systems

  32. EMC Symmetrix DMX Array • Direct Matrix Interconnect • Dynamic Global Memory • Enginuity Operating Environment • Processing Power • Flexible Back-End Configurations • Fault-tolerant Design Disk Storage Systems

  33. Symmetrix DMX Series Direct Matrix Architecture Disk Storage Systems

  34. Disk Director 16 S Disk Director 1 P P S S P P S S P P S S P P S Symmetrix DMX: Dual-ported Disk and Redundant Directors P = Primary Connection to Drive S= Secondary Connection for Redundancy Disk Storage Systems

  35. Physical Disk Physical Disk Physical Disk Physical Disk Physical Disk Configuring Symmetrix Logical Volumes (SLV) • Initial configuration of Symmetrix Logical Volumes is done via the Symmetrix Service Processor and the SymmWin interface/application • A configuration file (IMPL.BIN) is created and loaded on to the array • Subsequent configuration changes can be performed online using EMC ControlCenter (GUI) or by using Solutions Enabler (CLI) Symmetrix Service Processor Running SymmWin Application Disk Storage Systems

  36. Different Disk Director Disk Director Physical Drive LV 04B M2 Logical Volume 04B Physical Drive LV 04B M1 RAID1 – Symmetrix Logical Volume • RAID1 SLV • Data is written to two hyper volumes on two different physical disks which are accessed via two different disk directors • Host is unaware of data protection being applied Hyper Volumes Host Address Target = 1 LUN = 0 Disk Storage Systems

  37. Data Protection • Mirroring (RAID 1) • Highest performance, availability and functionality • Two hyper mirrors form one Symmetrix Logical Volume located on separate physical drives • Parity RAID (Not available on DMX3) • 3 +1 (3 data and 1 parity volume) or 7 +1 (7 data and 1 parity volume) • Raid 5 Striped RAID volumes • Data blocks are striped horizontally across the members of the RAID group ( 4 or 8 member group); parity blocks rotate among the group members • RAID 10 Mirrored Striped Mainframe Volumes • Dynamic Sparing • SRDF (Symmetrix Remote Data Facility) • Mirror of Symmetrix logical Volume maintained in a separate Symmetrix Disk Storage Systems

  38. Assigning Symmetrix Logical Volumes to Hosts • Configure Symmetrix Logical Volumes • Map Symmetrix Logical Volumes to Front-end ports • Performed via EMC ControlCenter or Solutions Enabler • Make Symmetrix Logical Volumes accessible to hosts • SAN Environment • Zone Hosts to Front-end ports • Perform LUN Masking • Can be performed via EMC ControlCenter or Solutions Enabler • LUN Masking information is maintained on the Symmetrix in the VCM Database (VCMDB) • LUN Masking information is also flashed to all the front-end directors Disk Storage Systems

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