Adaptec 2005S User Guide - Page 170
RAID 5EE Logical Drives
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Appendix D: Understanding RAID ● 169 RAID 5EE Logical Drives Note: RAID 5EE is an upgrade feature; if the RAID 5EE feature is locked, see Adding Enhanced Features on page 21 for information on purchasing a feature key. A RAID 5EE logical drive is similar to a RAID 5 logical drive except that it includes a distributed spare drive (see below) and must be built from a minimum of four disk drives. The maximum number of disk drives is sixteen. Unlike a hot spare (see page 90), a distributed spare is striped evenly across the disk drives with the stored data and parity data, and can't be shared with other logical disk drives. A distributed spare improves the speed at which the logical drive is rebuilt following a disk drive failure. A RAID 5EE logical drive protects your data and increases read and write speeds. However, capacity is reduced by two disk drives' worth of space, which is for parity data and spare data. In the example below, S represents the distributed spare, P represents the distributed parity data. Disk Drive 1 250 GB Drive Segment Size (Smallest Disk Drive) Disk Drive 2 250 GB Disk Drive 1 1 S ... P Disk Drive 3 400 GB Disk Drive 4 400 GB Disk Drives in Logical Drive Disk Drive 2 2 P ... 449 Disk Drive 3 S 3 ... S Not Used Unused Space: 150 GB Disk Drive 4 P 4 ... 500 Not Used Unused Space: 150 GB RAID 5EE Logical Drive = 500 GB plus Parity and Spare