Introduction to RAID
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RAID (Redundant Array of Inexpensive Disks) is a method of combining multiple hard disk drives into a logical unit to increase performance and provide fault tolerance. It duplicates and spreads data across disks so that if one disk fails, the data can still be accessed from another disk. RAID offers real-time data recovery when a drive fails to increase system uptime. It also improves performance by allowing multiple disks to work together simultaneously. Common RAID levels include RAID 0, 1, 5, and 10, each providing different balances of performance, capacity, and data protection.
Introduction to RAID
- 1. RAID — Begin With The Basics How Does RAID Work? RAID increases data protection and performance by What is RAID? duplicating and/or spreading data over multiple disks. DRIVE 1 RAID stands for Redundant Array of Inexpensive Disks. RAID is a method of logically treating Mirroring Mirroring & Striping several hard drives as one unit. It can offer fault tolerance and higher throughput levels than a single hard drive or group of independent hard drives. Duplicates data from primary Mirrors data that is striped, spread DRIVE 2 drive to secondary drive evenly across multiple disks Why Do We Need It? RAID provides real-time data recovery when a hard drive fails, increasing system uptime and DRIVE 1 DRIVE 1 DRIVE 3 availability while protecting against loss of data. Multiple drives working together also increase system performance. DRIVE 2 DRIVE 2 DRIVE 4 Levels of RAID DRIVE 1 DRIVE 3 RAID Level Description Minimum # of Drives Benefit RAID 0 Data striping (no data protection) 2 Highest performance DRIVE 2 DRIVE 4 RAID 1 Disk mirroring 2 Highest data protection RAID 1E Disk mirroring 3 Highest data protection for an odd number of disks RAID 5 Data striping with distributed parity 3 Best cost/performance balance for multi-drive environments RAID 5EE Data striping with distributed parity with 4 The cost/performance balance of RAID 5 without setting aside a dedicated hotspare disk hotspare integrated into the array RAID 6 Data striping with dual distributed parity 4 Highest fault tolerance with the ability to survive two disk failures RAID 10 Data striping of RAID 1 arrays 4 Highest performance with highest data protection RAID 50 Data striping of RAID 5 arrays 6 Increased capacity and performance for multi-array RAID 5 environments RAID 60 Data striping of RAID 6 arrays 8 Highest fault tolerance with the highest data protection Grow Your Business with PartnerPlus www.adaptec.com/partners/promo Email: adaptecsales@adaptec.com Call: 408-957-7279 or 800-442-7274
- 2. Types of RAID Implementation Glossary Type Description Advantages Ideal for Copyback Hot Spare: When a failed drive is replaced, data is automatically copied from the hot spare back to the replaced drive, allowing the hot spare to remain in the same spot. Software- Included in the operat- • Low price Best used for large Dual Drive Failure Protection (RAID 6, 60): Provides double redundancy and the ing system (OS), such block applications such ability to sustain two drive failures. Data is striped across at least 4 physical drives based as Windows®, NetWare, • Only requires a as data warehousing or and a second parity scheme is used to store and recover data. standard HBA and Linux. All RAID video streaming. Also Fault Tolerance: The ability of a system to continue to perform its functions even when functions are handled where servers have the one or more of its hard disk drives have failed. by the host CPU which available CPU cycles to can severely tax its manage the I/O inten- Hot Spare: A spare hard drive which will automatically be used to replace a failed ability to perform other sive operations certain member of a redundant disk array. computations. RAID levels require. Hot Swap: The ability to replace a failed member of a redundant disk array with a good drive without bringing down the server or interrupting transactions that involve the other Hardware- Processor-intensive • Data protection and Best used for small devices. based RAID operations are performance benefits block applications such Mirroring (RAID 1): Provides data protection by duplicating all data from a prmary off-loaded from the of RAID as transaction oriented drive onto a secondary drive. host CPU to enhance databases and web • More robust fault- Parity: A form of data protection used by RAID 5 to re-create the data of a failed drive. performance. Battery- servers. tolerance features back write back cache RAID 0: See “Striping.” and increased can dramatically performance RAID 1: See “Mirroring.” increase performance vs.software-based while minimizing risk of RAID 1E: See “Striped Mirroring.” RAID data loss. RAID 5: Combines data striping (for enhanced performance) with distributed parity (for data protection) to provide a recovery path in case of failure. External Connects to the • OS independent Build high-capacity hardware servervia a standard storage systems for RAID 5EE: See “Hot Space.” HBA or controller. RAID high-end servers RAID 6: See “Dual Drive Failure Protection.” functions are performed on a microprocessor RAID 10: Combines RAID 0 (data striping) and RAID 1 (disk mirroring). located on the external RAID 50: Combines multiple RAID 5 sets with data striping (RAID 0) to increase RAID controller inde- capacity and performance without adding disks to each RAID 5 array. pendent of the host. RAID 60: Combines multiple RAID 6 sets with data striping (RAID 0) to increase capacity and performance without adding disks to each RAID 6 array. Striped Mirror (RAID 1E): Combines data striping from RAID 0 with data mirroring from RAID 1 to extend RAID 1 data availability across an odd number of disks. Recommend Adaptec RAID Products Striping (RAID 0): Spreads data evenly over multiple drives to enhance performance. Adaptec by PMC delivers the industry’s most trusted RAID technology, Because there is no redundancy scheme, it does not provide data protection. built on two decades of pioneering RAID leadership. We offer the Hot Space (RAID 5EE): Provides the protection of RAID 5 and adds a hot spare disk to industry’s most advanced data protection, including RAID 0, RAID 1, the array. This extra drive enhances RAID 5 performance with higher I/Os per second. RAID 1EE, RAID 5, RAID 6, RAID 10, RAID 50, RAID 60, and Copyback Hot Spare. For more information: www.adaptec.com © Copyright PMC-Sierra, Inc. 2010. All rights reserved. PMC, PMC-SIERRA and Adaptec are registered trademarks of PMC-Sierra, Inc. “Adaptec by PMC” is a trademark of PMC-Sierra, Inc. Other product and company names mentioned herein may be trademarks of their respective owners. For a complete list of PMC-Sierra trademarks, see www.pmc-sierra.com/legal. INTRO-RAID-090310