RAID 5 Pros: Pros: Pros: Pros: (rotated Balanced load. Single loss Single loss does One additional disk parity) Potential for better survivable; not prevent access. required. read response requests Three-disk times, throughput, might still corrupt. minimum. and concurrency. Cons: Up to 75% write performance hit due to RMW. Read performance degrades in failure Cons: mode. Multiple losses All sectors that Cons: prevent access to must be read for Multiple losses entire array. reconstruction; affect entire array. To speed major slowdown. After a single loss, reconstruction, Danger of data in array is vulnerable application access invalid state after until reconstructed. might be slowed or power loss and stopped. recovery. RAID 6 Pros: Pros: Pros: Pros: (two Balanced load. Single loss Single loss does Two additional separate Potential for better survivable; "inflight" not prevent access. disks required. erasure read response write requests Five-disk minimum. codes) times, throughput, might still corrupt. and concurrency. Cons: Up to 83% performance hit due to multiple RMW. Read performance degrades in failure Cons: mode. >2 losses prevent All sectors must be Cons: access to entire read for >2 losses array. reconstruction: affect entire To speed major slowdown. 2 losses, array reconstruction, Danger of data in is vulnerable until application access invalid state after reconstructed. might be slowed or power loss and stopped. recovery. The following are sample uses for various RAID levels: JBOD: Concurrent video streaming. RAID 0: Temporary or reconstructable data, workloads that tend to develop hot spots in the data, and workloads with high degrees of unrelated concurrency. RAID 1: Database logs, and critical data and concurrent sequential streams. RAID 0+1: A general-purpose combination of performance and reliability for critical data, workloads with hot spots, and high-concurrency workloads. RAID 5: Web semicritical data, workloads without small writes, scenarios where capital and operating costs are an overriding factor, and read-dominated workloads.
RAID 5 (rotated parity) Pros: Balanced load. Potential for better read response times, throughput, and concurrency. Cons: Up to 75% write performance hit due to RMW. Read performance degrades in failure mode. All sectors that must be read for reconstruction; major slowdown. Danger of data in invalid state after power loss and recovery. Pros: Single loss survivable; requests might still corrupt. Cons: Multiple losses affect entire array. After a single loss, array is vulnerable until reconstructed. Pros: Single loss does not prevent access. Cons: Multiple losses prevent access to entire array. To speed reconstruction, application access might be slowed or stopped. Pros: One additional disk required. Three-disk minimum. RAID 6 (two separate erasure codes) Pros: Balanced load. Potential for better read response times, throughput, and concurrency. Cons: Up to 83% performance hit due to multiple RMW. Read performance degrades in failure mode. All sectors must be read for reconstruction: major slowdown. Danger of data in invalid state after power loss and recovery. Pros: Single loss survivable; "inflight" write requests might still corrupt. Cons: >2 losses affect entire 2 losses, array is vulnerable until reconstructed. Pros: Single loss does not prevent access. Cons: >2 losses prevent access to entire array. To speed reconstruction, application access might be slowed or stopped. Pros: Two additional disks required. Five-disk minimum. The following are sample uses for various RAID levels: JBOD: Concurrent video streaming. RAID 0: Temporary or reconstructable data, workloads that tend to develop hot spots in the data, and workloads with high degrees of unrelated concurrency. RAID 1: Database logs, and critical data and concurrent sequential streams. RAID 0+1: A general-purpose combination of performance and reliability for critical data, workloads with hot spots, and high-concurrency workloads. RAID 5: Web semicritical data, workloads without small writes, scenarios where capital and operating costs are an overriding factor, and read-dominated workloads.
WS08PerformanceTuningGuideFinal_En.docx