RAID storage systems have been in use since the early 1990's. Recently, however, as the demand for huge amounts of on-line storage has increased, RAID has once again come into focus. This report reviews the history of RAID, as well as where and how RAID systems fit in the storage hierarchy of an Enterprize Computing System (EIS). We describe the known RAID configurations and the advantages and disadvantages of each. Since the focus of our research is on the performance of RAID systems we devote a section to the various factors which affect RAID performance. Modelling RAID systems for their performance analysis is the topic of the next section and we report on the issues as well as briefly describe one simulator, RAIDframe, which has been developed. We conclude with section which describes the current open research questions in the area
