HP 226593-B21 Smart Array 5i Plus Controller and Battery Backed Write Cache En - Page 85
fault tolerance., RAID 5-Distributed Data Guarding
UPC - 720591665913
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Drive Arrays and Fault Tolerance A1 L1 L2 A2 L3 L4 L5 Figure C-4: Two arrays (A1, A2) containing five logical drives spread over five physical drives Each logical drive in an array is distributed over all of the physical drives within the array. A logical drive can also extend over more than one port on the same controller, but it cannot extend over more than one controller. Drive failure, although rare, is potentially catastrophic. In Figure C-4, for example, failure of any physical drive causes all logical drives in the same array to fail, and all data on the drives is lost. To protect against data loss due to physical drive failure, logical drives are configured with fault tolerance. There are several fault-tolerance methods; those supported by current Compaq controllers (and described in the "Fault Tolerance Methods" section) are: • RAID 0-Data Striping only (no fault tolerance) • RAID 1+0-Drive Mirroring • RAID 5-Distributed Data Guarding C-4 Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache Enabler User Guide