OnLine mirroring, SCO 5

We are about to buy a new server for running mission critical applications and would appreciate any input from anyone with any experience. Max. downtime due to any deffect must be kept to less than 4 hours. We plan to buy an Intel based server running SCO Unix. We have several successfull installations of this type. There will be nothing but an Informix OnLine db engine and our 4GL programs running on this machine. Initially it will be a single 100MHz Pentium, but with option to upgrade to 4 x 133 MHz Pentiums and possibly P6 later. Now however we plan to use mirroring. We haven't done that before and would like to here any information/hints/stories about it, particularly on SCO machines of course. The disk hardware is hot swap. The main board of the machine is made by Intel, while our supplier suggests Mylex disk controllers. We will run the db on raw devices. Can we expect to pull out a bad disk, put in a new one and continue running without user interruption? Any real experiences, tests or ideas? We plan to utilize Informix OnLine mirroring due to reports of better performance than RAID. With RAID the supplier say we can utilize the hot swap option without problems. Perhaps RAID level 0 (plain mirroring) is better than using OnLine? Initially there will be two pairs of 4GB disk drives with mirrored data (root and log on one and user data on the other pair). Later this will be expanded to several more pairs. Unix and user files will be on a separate 4GB disk. We currently use OnLine 7.10.UCx and 4GL 6.00.UE3 on SCO 3.2.4.2 It seems Informix has stopped all new releases on this version of SCO. Does anybody have any experience with SCO 5 (3.2.5.0??) and Informix OnLine/4GL? Is it stable and free of defects (at the operating system level as well as Informix OnLine). (Free..??.. that means not too many or severe defects.) Nils.Myklebust@ccmail.telemax.no NM-data, Dalsbergstien 7, N-0170 Oslo, Norway My opinions are those of my company