Home | Contents | Help   Raidhelp   Welcome to the first online version of RaidHelp, a simple on-line information system concentrating on explaining in layman terms, with as little jargon as realistically possible, certain aspects of storage technology and techniques.         The objective is to help explain various technologies, their implementations and planning, together with the advantages and disadvantages of each technology, in particular the subject of RAID technology. The guide can be viewed on-line at this site.     Introduction : Introduction to RAID Exactly what is RAID and EDAP? EDAP Defined RAID Defined Objectives of a RAID System Explaining the different RAID levels. The major difference between striping and mirroring, dispersed parity and dedicated parity drives. Which RAID level is suitable for your data type. Defining RAID Levels RAID 0 RAID 1 RAID 1/0 RAID 2 RAID 3 RAID 4 RAID 5 RAID 6 The components of a RAID disk array system and how they all fit together to give you data protection and high performance. The different ways you can build the same RAID system from very different parts. The Controller Enclosures Logical Drives & Volumes Physical Storage Media Memory & Cache Spare & Standby Drives SAFTE Software RAID PCI-based RAID Auto Rebuilding Hot & Warm Swap Ability Storing data safely on disks - data integrity and parity - the most important aspect of an array. Understanding Parity RAID Parity Simple Parity Calculations XOR Parity Calculations Performance expectations & data transfer considerations. How it works in the real world. Performance Considerations The Data Pipeline Interface Considerations Genuine Data Throughput . . . and the Misconceptions Selecting & understanding different interfaces. Explanation of how the interface you use can make a huge difference to the results and the performance of your RAID system. The Interface Decision Multi-threaded I/O Interfaces The SCSI Interface SCSI Command Sets SCSI Cabling & Connectors SCSI ID & LUN Configuration SCSI Ultra2 LVD Fibre Channel Interface Fibre Channel Cabling & Connectors IDE/ATA Interface Running and maintaining the system. What happens when something fails? Four Conditional States of EDAP/RAID systems Protected Volatile Critical Failed Data distribution. Three stages of I/O Processing Redundancy - preparing for component failure. There is no such thing as being too safe. Controller Redundancy Active-Active Architectures Active-Passive Architectures Clustered Servers     Raidhelp   RAIDhelp© Copyright 1999-2004 Antony Kershaw