Appendix C: Selecting the Best RAID Level ● 166RAID 6 Logical DrivesA RAID 6 logical drive—also referred to as dual drive failure protection—is similar to a RAID 5logical drive because it uses data striping and parity data to provide redundancy. However,RAID 6 logical drives include two independent sets of parity data instead of one. Both sets ofparity data are striped separately across all disk drives in the logical drive.RAID 6 logical drives provide extra protection for your data because they can recover from twosimultaneous disk drive failures. However, the extra parity calculation slows performance(compared to RAID 5 logical drives).RAID 6 logical drives must be built from at least four disk drives. Maximum stripe sizedepends on the number of disk drives in the logical drive.RAID 60 Logical DrivesSimilar to a RAID 50 logical drive (see page 165), a RAID 60 logical drive—also referred to asdual drive failure protection— is built from at least eight disk drives configured as two or moreRAID 6 logical drives, and stripes stored data and two sets of parity data across all disk drives inboth RAID 6 logical drives.Two sets of parity data provide enhanced data protection, and striping improves performance.RAID 60 logical drives also provide high data transfer speeds.Disk Drive 1Disk Drive 2Disk Drive 3Disk Drive 4250 GB250 GB400 GB400 GBDrive Segment Size (Smallest Disk Drive)Disk Drive 2Disk Drive 3Disk Drive 4Disk Drive 11 P1 ... P22 P2 ... 449P1 3 ... P1P2 4 ... 500Unused Space = 150 GBDisk Drives in Logical DriveUnused Space = 150 GB= 500 GB plus Parity (P1 & P2)RAID 6Logical Drive
