Lenovo ThinkServer RD240 MegaRAID SAS Software User Guide - Page 52

RAID 5 addresses the bottleneck issue for random I/O operations. Because each drive contains both data and parity, numerous writes can take place concurrently. Table 2.7 provides an overview of RAID 5. Figure 2.7 provides a graphic example of a RAID 5 drive group. Table 2.7 RAID 5 Overview Uses Strong Points Weak Points Drives Provides high data throughput, especially for large files. Use RAID 5 for transaction processing applications because each drive can read and write independently. If a drive fails, the RAID controller uses the parity drive to recreate all missing information. Use also for office automation and online customer service that requires fault tolerance. Use for any application that has high read request rates but low write request rates. Provides data redundancy, high read rates, and good performance in most environments. Provides redundancy with lowest loss of capacity. Not well-suited to tasks requiring lot of writes. Suffers more impact if no cache is used (clustering). Drive performance will be reduced if a drive is being rebuilt. Environments with few processes do not perform as well because the RAID overhead is not offset by the performance gains in handling simultaneous processes. 3 to 32 Figure 2.7 RAID 5 Drive Group with Six Drives Segment 1 Segment 7 Segment 13 Segment 19 Segment 25 Parity (26-30) Segment 2 Segment 8 Segment 14 Segment 20 Parity (21-25) Segment 26 Segment 3 Segment 9 Segment 15 Parity (16-20) Segment 21 Segment 27 Segment 4 Segment 10 Parity (11-15) Segment 16 Segment 22 Segment 28 Note: Parity is distributed across all drives in the drive group. Segment 5 Parity (6-10) Segment 11 Segment 17 Segment 23 Segment 29 Parity (1-5) Segment 6 Segment 12 Segment 18 Segment 24 Segment 30 2-20 Introduction to RAID