Adaptec 6405E Installation And User Manual

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Adaptec 6405E Installation And User Manual Manual pdf 97 page image

Appendix B: Understanding RAID ● 96Understanding Drive SegmentsA drive segment is a disk drive or portion of a disk drive that is used to create an array. A diskdrive can include both RAID segments (segments that are part of an array) and availablesegments. Each segment can be part of only one logical device at a time. If a disk drive is notpart of any logical device, the entire disk is an available segment.Non-redundant Arrays (RAID 0)An array with RAID 0 includes two or more disk drives and provides data striping, where datais distributed evenly across the disk drives in equal-sized sections. However, RAID 0 arrays donot maintain redundant data, so they offer no data protection.Compared to an equal-sized group of independent disks, a RAID 0 array provides improved I/Operfor mance.Drive segment size is limited to the size of the smallest disk drive in the array. For instance, anarray with two 250 GB disk drives and two 400 GB disk drives can create a RAID 0 drivesegment of 250 GB, for a total of 1000 GB for the volume, as shown in this figure.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 5 ... 9972 6 ... 9983 7 ... 9994 8 ... 1000Unused Space = 150 GBDisk Drives in Logical Drive RAID 0 Logical Drive = 1000 GBUnused Space = 150 GB