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RAID CONCEPT
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RAID CONCEPT

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  • 1. RAID Concepts Engenio Storage Group Internal RAID 2008
  • 2. RAID Concepts
    • Objective:
    • At the end of this presentation you will be able to …
      • Discuss basic RAID technology market positioning
      • Explain the inherent advantages of using RAID
      • Identify appropriate RAID levels to use for specific platforms and applications
  • 3. What is RAID?
    • RAID stands for an redundant array of independent drives
    • Intelligently manages drives in unison performing data read/write algorithms across drives delivering
      • High levels of protection against downtime and data loss (mirroring)
      • Larger storage volumes achievable
      • Improved performance (striping)
  • 4. RAID Level Overview
    • Selecting the proper RAID level for a specific data storage application requires consideration be given to the benefits of each
    • LSI Supported
    • RAID 0 (1 to 32 disks)
    • RAID 1 (2 disks)
    • RAID 5 (3 to 32 disks)
    • RAID 10 (4 to 16 disks)
    • RAID 50 (6 to 60 disks)
    • RAID 6
    • Use
    • Video/Audio streaming
    • OS boot
    • Transaction/Web server
    • Database
    • Data warehousing
    • Large capacity disk arrays
  • 5. RAID 0 - Striping
    • Striping - writes data across multiple drives
    • Involves partitioning each drive storage space into stripes that can vary in size from 2 KB to 1 MB.
    • These stripes are interleaved in a repeated sequential manner.
    Definition No Fault Tolerance Minimum 1 / Maximum 64 Drives
    • Non-critical data requiring high performance
    • Environments that do not require fault tolerance
    Uses
    • No fault tolerance: If any drive in the array fails, all data is lost
    Drawbacks
    • High data throughput, especially for large files
    • No capacity loss penalty for parity.
    Benefits
  • 6. RAID 0
  • 7. RAID 1: Mirroring
    • Mirroring - writes duplicate data to more than one (usually two) drives
    • Protects against data loss in the event of a device failure
    Definition Yes Fault Tolerance 2 Drives
    • If availability is critical
      • Use RAID 1 for small databases or any other environment that requires fault tolerance but small capacity
    Uses
    • Expensive: Requires two drives for the storage space of one drive
    • Reduced Performance during drive rebuilds.
    Drawbacks
    • Provides 100% data redundancy
    • Should one drive fail, the controller switches reads and writes to the other drive.
    Benefits
  • 8. RAID 1
  • 9. RAID 5 : Striping with Rotational Parity
    • Striping with rotational parity - blocks of data and parity information is stripped across all drives
    • RAID level 5 is the most popular configuration, providing striping as well as parity for error recovery
    Definition Yes Fault Tolerance Minimum 3 Drives
    • Any application that has high read request rates and average write request rates
    • Transaction servers, web servers, data mining applications, exchange servers
    Uses
    • Cannot match RAID 0 in write performance due to processing required to compute parity
      • While a controller is rebuilding a drive, users will experience reduced performance if reading or writing data
    Drawbacks
    • Uses one disk worth of space to achieve data redundancy
      • If a hot spare is available, it can perform a rebuild automatically
    Benefits
  • 10. RAID 5
  • 11. RAID 10 : Spanning two RAID 1’s Spanning two RAID 1’s - writing duplicate data to more than one pair of drives to protect against data loss in the event of a up to two disk failures (one per array) Definition Yes Fault Tolerance Minimum 4 / Maximum 16 Drives
    • Environments that require 100% redundancy of mirroring (RAID 1) and the enhanced I/O performance of stripping (RAID 0)
    • Ideal for smaller organizations needing a high degree of fault tolerance and moderate to medium capacity.
    Uses
    • Requires half the available disk space for data redundancy
      • Same as RAID level 1.
    Drawbacks
    • Optimized for both fault tolerance and performance
    • Provides both high data transfer rates and complete data redundancy
    Benefits
  • 12. RAID 50 : Spanning two RAID 5’s Data is “striped” across multiple drive groups (super drive group). For data redundancy, drives are encoded with rotated XOR redundancy. RAID 50 provides the features of both RAID 0 and RAID 5. RAID 50 includes both parity and disk striping across multiple drives. Definition Yes Fault Tolerance Minimum 6 Drives RAID 50 works best when used with data that requires high reliability, high request rates, and high data transfer and medium to large capacity. Uses Requires at least twice as many parity drives as a single RAID 5. Drawbacks RAID 50 provides high data throughput, data redundancy, and very good performance. Benefits
  • 13. RAID 50
  • 14. RAID 0+1 Enhanced Mirroring The controller combines the performance of data striping (RAID 0) and the fault tolerance of disk mirroring (RAID 1). Data is striped across multiple drives and duplicated on another set of drives. Definition Yes Fault Tolerance Minimum 4 Drives If a drive fails, the controller uses the parity drive to recreate all missing information. Uses Requires half the available disk space for data redundancy, the same as RAID level 1. Drawbacks Optimizes for both fault tolerance and performance. Provides excellent performance for all data needs. May be simultaneously used with other RAID levels in an array. Benefits
  • 15. RAID 0+1
  • 16. RAID 1E Enhanced Mirroring
    • Enhanced mirroring - combines mirroring with data striping
    • The first set of stripes are the data, and the second set of stripes are mirrors of the first data stripe contained within the next logical drive.
    Definition Yes Fault Tolerance Minimum 3 Drives
    • When array availability is most important
    • For small databases or any other environment that requires fault tolerance but small capacity
    Uses
    • 50% storage efficiency
    Drawbacks
    • Shares the characteristics of RAID 1, but allows more than two drives, including odd numbers of drives
    • If one of the drives fails, the controller switches read and write requests to the remaining functional drives in the RAID level-1E array.
    Benefits
  • 17. RAID 1E
  • 18. JBOD: Single Drive Control No Fault Tolerance
    • Works best when used if you have odd sized drives and you want to combine them to make one big drive
    Uses
    • Decreases performance because of the difficulty in using drives concurrently or to optimize drives for different uses
    Drawbacks Single drive control - the ability to combine odd size drives using all of the capacity of the drives. Benefits
  • 19. RAID 6 : Striping with Dual Rotational Parity
    • Distributed parity – disk striping and two independent parity blocks per stripe
    • Can survive the loss of two disks without losing data
    Definition Yes Fault Tolerance Minimum 3 Drives
    • Any application that has high read request rates and average write request rates
    • Transaction servers, web servers, data mining applications, exchange servers
    Uses
    • Requires two sets of parity data for each write operation, resulting in significant decrease in write performance
    • Additional costs because of the extra capacity required by using two parity blocks per stripe
    Drawbacks
    • Data redundancy, high read rates, and good performance
    Benefits
  • 20. RAID 6
  • 21. RAID Level Summary
    • RAID 0: Fastest and most efficient level but offers no fault tolerance
    • RAID 1: Performance-critical, fault tolerant environments, but requires 2X storage
    • RAID 5: Best choice for multi-user environments which are not write performance sensitive
    • RAID 10: Ideal for e nvironments that require 100% redundancy with enhanced I/O performance of stripping and can afford such an investment
    • RAID 50: Works best when used with data that requires high reliability, high request rates, and high data transfer rates
    • RAID 0+1: Optimal for applications needing both fault tolerance and performance. Provides excellent but additional capacity investment
    • RAID 1E: Great choice for small databases or any other environment that need fault tolerance but have small capacity requirements
    • RAID 6: Ideal for organizations of all sizes requiring d ata redundancy, high read rates, and good performance