EMC CX500I Configuration Guide - Page 50

RAID Types and Trade-offs Sample Applications for RAID Types This section describes some types of applications in which you would want to use a RAID 5 Group, RAID 3 Group, RAID 1 mirrored pair, RAID 0 Group (nonredundant array), RAID 1/0 Group, or individual unit. RAID 5 Group (individual access array) - Useful as a database repository or a database server that uses a normal or low percentage of write operations (writes are 33 percent or less of all I/O operations). Use a RAID 5 Group where multitasking applications perform I/O transfers of different sizes. Write caching can significantly enhance the write performance of a RAID 5 Group. For example, a RAID 5 Group is suitable for multitasking applications that require a large history database with a high read rate, such as a database of legal cases, medical records, or census information. A RAID 5 Group also works well with transaction processing applications, such as an airline reservations system, where users typically read the information about several available flights before making a reservation, which requires a write operation. You could also use a RAID 5 Group in a retail environment, such as a supermarket, to hold the price information accessed by the point-of-sale terminals. Even though the price information may be updated daily, requiring many write operations, it is read many more times during the day. RAID 3 Group - A RAID 3 Group (parallel access array) works well with a single-task application that uses large I/O transfers (more than 64 Kbytes), aligned to start at a disk address that is a multiple of 2 Kbytes from the beginning of the logical disk. RAID 3 Groups can use SP memory to great advantage without the second SP and battery backup unit required for storage-system caching. You might use a RAID 3 Group for a single-task application that does large I/O transfers, like a weather tracking system, geologic charting application, medical imaging system, or video storage application. RAID 1 mirrored pair - A RAID 1 mirrored pair is useful for logging or record-keeping applications because it requires fewer disks than a RAID 0 Group (nonredundant array) and provides high availability and fast write access. Or you could use it to store daily updates to a database that resides on a RAID 5 Group, and then, during off-peak hours, copy the updates to the database on the RAID 5 Group. 2-20 EMC CLARiiON CX300, CX500, CX500i, and CX700 Storage Systems Configuration Planning Guide