Adaptec 5805 Installation And User Manual

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Adaptec 5805 Installation And User Manual Manual pdf 79 page image

Appendix B: Understanding RAID ● 79RAID 5EE ArraysA RAID 5EE array—also known as a hot space—is similar to a RAID 5 array except that itincludes a distributed spare drive and must be built from a minimum of four disk drives.Unlike a hot spare, a distributed spare is striped evenly across the disk drives with the storeddata and parity data, and can’t be shared with other logical disk drives. A distributed spareimproves the speed at which the array is rebuilt following a disk drive failure.A RAID 5EE array protects your data and increases read and write speeds. However, capacity isreduced by two disk drives’ worth of space, which is for parity data and spare data.In this figure, S represents the distributed spare, P represents the distributed parity data.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 S ... P2 P ... 449S 3 ... SP 4 ... 500Unused Space = 150 GBDisk Drives in Logical Drive Based on the drive segment sizes used:RAID 5EE Logical Drive = 500 GB plus parityand hot spare.Unused Space = 150 GB