Adaptec AEC-4412B User Manual

Also see for AEC-4412B: Technical specifications

Contents

AEC-4412B/7412B User’s GuideStock Number: 511640-00 Rev B Page: A-1Print Spec Number: 497358-00Current Date: 3/19/98 ECN Date: 3/20/98A-1AArray BasicsAdaptec’s AEC-4412B/7412B External RAID Controllers let you setup and manage disk arrays. A disk array is a group of disks thatappears to the system as a single virtual disk. This is accomplishedthrough software resident in the RAID controller. RAID (RedundantArray of Independent Disks) refers to disk arrays in which part ofthe array storage capacity may be used to store redundant informa-tion. The redundant information lets you restore user data if a diskin the array fails.The host system views the AEC-4412B/7412B controllers as a singleSCSI disk drive. It is actually an array of physical disks behind aRAID controller. The AEC-4412B/7412B therefore is managed bysoftware to appear as a single very large physical disk. Dependingon the array type, the virtual disk has advantages in fault-tolerance,cost, performance, or a combination of these. This chapter explainsthe different array types and the disk requirements for each type.Array TypesArray types are defined by their RAID level, a number from 0through 5 (a higher RAID level does not necessarily indicate ahigher level of performance or fault-tolerance). AEC-4412B/7412BRAID controllers let you create the types of arrays that have provento be the most useful for RAID applications: RAID 0, 1, 1/0 (alsoknown as mirrored), 3, 4, and 5.