Lenovo ThinkServer RD240 MegaRAID SAS Software User Guide - Page 48
Enclosure Management, 2.5 RAID Levels, 2.5.1 Summary of RAID Levels
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2.4.19 Enclosure Management Enclosure management is the intelligent monitoring of the disk subsystem by software and/or hardware. The disk subsystem can be part of the host computer or can reside in an external disk enclosure. Enclosure management helps you stay informed of events in the disk subsystem, such as a drive or power supply failure. Enclosure management increases the fault tolerance of the disk subsystem. 2.5 RAID Levels The RAID controller supports RAID levels 0, 00, 1, 5, 6, 10, 50, and 60. The supported RAID levels are summarized in the following section. In addition, it supports independent drives (configured as RAID 0 and RAID 00.) The following sections describe the RAID levels in detail. 2.5.1 Summary of RAID Levels RAID 0 uses striping to provide high data throughput, especially for large files in an environment that does not require fault tolerance. RAID 1 uses mirroring so that data written to one drive is simultaneously written to another drive. This is good for small databases or other applications that require small capacity but complete data redundancy. RAID 5 uses disk striping and parity data across all drives (distributed parity) to provide high data throughput, especially for small random access. RAID 6 uses distributed parity, with two independent parity blocks per stripe, and disk striping. A RAID 6 virtual drive can survive the loss of two drives without losing data. A RAID 6 drive group, which requires a minimum of three drives, is similar to a RAID 5 drive group. Blocks of data and parity information are written across all drives. The parity information is used to recover the data if one or two drives fail in the drive group. A RAID 00 drive group is a spanned drive group that creates a striped set from a series of RAID 0 drive groups. 2-16 Introduction to RAID