Himanshu Kumar Yogesh Patel - Rochester Institute of ...Himanshu Kumar Yogesh Patel. Outline...
Transcript of Himanshu Kumar Yogesh Patel - Rochester Institute of ...Himanshu Kumar Yogesh Patel. Outline...
OutlineHistory of RAIDWhat is RAID & Why it is requiredReliability TermsRAID ConfigurationsModern RAID ConfigurationsApplicationsProblems with RAID
History of RAIDIn 1977, David Patterson, Garth Gibson & Randy KatzOriginally 5 RAID LevelsRole of RAB (RAID Advisory Board)
Introduction to RAIDWhat is RAID?
Redundant Array of Independent DiskStorage Technology to Improve Reliability , Flexibility & PerformanceStorage virtualization of disk
Reliability TermsFailure RateMean Time to Data LossMean Time to Data RecoveryUnrecoverable Bit Error RateWrite Cache Reliability
RAID 0Focused on PerformanceZero RedundancyBlock Level StrippingCapacity = n*min(disk size)MTTFgroup = MTTFdisk/nApplications
RAID 1Drives Mirror of each otherNo Parity CalculationImproves data reliability or availabilityCapacity= min(disk size)P(dual failure) = P(single drive)2
Applications
RAID 3Three disks for data & Fourth for storing parity.Cannot Handle multiple request.Capacity = min(disksize)*(n‐1)More reliable than RAID 0 but lower performanceByte level Stripping
RAID 4• Block level stripping so multiple request• Capacity = min(disk size) * ( n – 1 )• Lower write performance than RAID 0
RAID 5• Better performance than RAID 4.• Parity is written on all drives.•Reliability better than RAID 4.•Hot Spare Drive•URE for large capacity
RAID 6• Address URE of RAID 5• Better Reliability• Capacity = min ( disk size ) * ( n – 2 )• Lower write performance than RAID 5
Nested/Hybrid RAIDCombination of Two or more Standard RAID LevelRAID 01RAID 10RAID 03RAID 30RAID 05RAID 50RAID 06RAID 60
Failure‐resistantPrevent and protect against data loss due to drive failureMaintaining a distributed system
Failure‐tolerantAutomatic Disk Swapping Checking environment and other physical failuresCache Failure
Problems with RAIDCorrelated failuresAtomicityWrite cache reliabilityEquipment compatibilityData recovery in the event of a failed arrayDrive error recovery algorithmsRecovery time is increasingOperator skills, correct operationOther problems