RAID was designed to be a Redundant Array of INEXPENSIVE Disks - but the originators realised that the goals they were trying to achieve - of data protection and performance, werent acheivable with inexpensive disks.Hence the 'I' in the acronym now stands for Independent!! RAID is basically a data protection scheme. RAID-0, which is actually striping of data across n disks for performance, was not originally part of the RAID scheme. To acheive protection, you could go from high cost RAID 1, which duplicates all data, to doing parity calculations so as to reduce your costs. 'Software' or "hardware' RAID tells you whether this parity calculation is being done by software(that uses host cpu cycles) or a dedicated processor in the disk controller(called a RAID controller). It is this parity calculation that causes the drop in performance for software RAID. For all server environments, it is recommended to go for hardware RAID controllers. As for the performance part of it - to reduce the number of disk reads and writes - a cache is used in the disk controller. But then that is another story......
regds, kishor __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/ -- _______________________________________________ http://mm.ilug-bom.org.in/mailman/listinfo/linuxers
