EMC CX500I Configuration Guide - Page 48
Guidelines for RAID Groups, Use a RAID 5 Group individual access array
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RAID Types and Trade-offs Guidelines for RAID Groups To decide when to use a RAID 5 Group, RAID 3 Group, mirror (that is, a RAID 1 mirrored pair or RAID 1/0 Group, a RAID 0 Group, individual disk unit, or hot spare), you need to weigh these factors: ◆ Importance of data availability ◆ Importance of performance ◆ Amount of data stored ◆ Cost of disk space The following guidelines will help you decide on RAID types. Use a RAID 5 Group (individual access array) for applications where ◆ Data availability is very important. ◆ Large volumes of data will be stored. ◆ Multitask applications use I/O transfers of different sizes. ◆ Excellent read and good write performance is needed (write performance is very good with write caching). ◆ You want the flexibility of multiple LUNs per RAID Group. Use a RAID 3 Group (parallel access array) for applications where ◆ Data availability is very important. ◆ Large volumes of data will be stored. ◆ A single-task application uses large I/O transfers (more than 64 Kbytes). The operating system must allow transfers aligned to start at disk addresses that are multiples of 2 Kbytes from the start of the LUN. Use a RAID 1 mirrored pair for applications where ◆ Data availability is very important. ◆ Speed of write access is important and write activity is heavy. Use a RAID 1/0 Group (mirrored nonredundant array) for applications where ◆ Data availability is critically important. ◆ Overall performance is very important. 2-18 EMC CLARiiON CX300, CX500, CX500i, and CX700 Storage Systems Configuration Planning Guide