Re: Compaq tell me I cannot use hardware raid and raw disks with informix

"Dennis JR Harding" <dennish@wpr.co.za> offerred: :Further, it is advisable to use the Informix mirroring method above any :other logical method. Online 7 will optimize to use mirror disks with the :primary disk in executing SELECTS, so doing also increasing performance. Be careful here. The optimization is not all that sophisticated. All it does is break the chunk "logically" in half, so read requests from the first half of the chunk are satisfied from the primary; read requests from the second half are satisfied from the mirror. If the chunk is not fully used, or worse yet, less than half used, there would be little to no appreciable performance impact. Also, one has to bear in mind that the cost of raid 5 is typically much lower than mirroring, as you don't require 100% disk overhead as with mirroring. Cost of hardware is still an issue for a lot of folks. While it is certainly easier to use straight disks rather than a raid config (as it makes it very easy to map dbspace to physical disk that way), Informix engineers have done some testing in the past to determine how online and raid work together. I don't have any copies of the results handy, but I do recall that it was reported that the two were not incompatible. I believe the recommendation was to make the chunk size == slice size or somesuch. Dave ********** "Everybody plays the fool, sometimes."