Intel AFCSASRISER User Guide - Page 33

RAID Level Performance 5 RAID 5 provides high data throughput, especially for large files. Use this RAID level for any application that requires high read request rates, but low write request rates, such as transaction processing applications, because each drive can read and write independently. Since each drive contains both data and parity, numerous writes can take place concurrently. In addition, robust caching algorithms and hardware based exclusive-or assist make RAID 5 performance exceptional in many different environments. Parity generation can slow the write process, making write performance significantly lower for RAID 5 than for RAID 0 or RAID 1. Disk drive performance is reduced when a drive is being rebuilt. Clustering can also reduce drive performance. Environments with few processes do not perform as well because the RAID overhead is not offset by the performance gains in handling simultaneous processes. 6 RAID 6 works best when used with data that requires high reliability, high request rates, and high data transfer. It provides high data throughput, data redundancy, and very good performance. However, RAID 6 is not well suited to tasks requiring a lot of writes. A RAID 6 virtual disk has to generate two sets of parity data for each write operation, which results in a significant decrease in performance during writes. Disk drive performance is reduced during a drive rebuild. Environments with few processes do not perform as well because the RAID overhead is not offset by the performance gains in handling simultaneous processes. 10 RAID 10 works best for data storage that need the enhanced I/O performance of RAID 0 (striped arrays), which provides high data transfer rates. Spanning increases the size of the virtual volume and improves performance by doubling the number of spindles. The system performance improves as the number of spans increases (the maximum number of spans is eight). As the storage space in the spans is filled, the system stripes data over fewer and fewer spans and RAID performance degrades to that of a RAID 1 or RAID 5 array. 50 RAID 50 works best when used with data that requires high reliability, high request rates, and high data transfer. It provides high data throughput, data redundancy, and very good performance. Spanning increases the size of the virtual volume and improves performance by doubling the number of spindles. The system performance improves as the number of spans increases (the maximum number of spans is eight). As the storage space in the spans is filled, the system stripes data over fewer and fewer spans and RAID performance degrades to that of a RAID 1 or RAID 5 array. 60 RAID 60 works best when used with data that requires high reliability, high request rates, and high data transfer. It provides high data throughput, data redundancy, and very good performance. Spanning increases the size of the virtual volume and improves performance by doubling the number of spindles. The system performance improves as the number of spans increases (the maximum number of spans is eight). As the storage space in the spans is filled, the system stripes data over fewer and fewer spans and RAID performance degrades to that of a RAID 1 or RAID 6 array. RAID 60 is not well suited to tasks requiring a lot of writes. A RAID 60 virtual disk has to generate two sets of parity data for each write operation, which results in a significant decrease in performance during writes. Disk drive performance is reduced during a drive rebuild. Environments with few processes do not perform as well because the RAID overhead is not offset by the performance gains in handling simultaneous processes. Maximizing Storage Capacity Storage capacity is an important factor when selecting a RAID level. There are several variables to consider. Striping alone (RAID 0) requires less storage space than mirrored data (RAID 1 or IME) or distributed parity (RAID 5 or RAID 6). RAID 5, which provides redundancy for one drive failure without duplicating the contents of entire disk drives, requires less space then RAID 1. Table 11 explains the effects of the RAID levels on storage capacity. Intel® RAID Software User's Guide 21