Q:multiple mirrors

Hi all, though it has been mentioned somewhere that Informix now supports more than two mirrored chunks I haven't found out how to implement this. Could you please point me to appropriate documentation on explain in the list? thanks for your attention, Ivars Strazdins SRS network administrator

Ivars Strazdins wrote: > > Hi all, > > though it has been mentioned somewhere that Informix now supports more than > two mirrored chunks I haven't found out how to implement this. Could you > please point me to appropriate documentation on explain in the list? I think that you are suffering from some confusion stemming from a post I made several months ago. What I was trying to say, badly, is that Informix now (V7.3x) directly supports using OS archive software to back up the disk chunks directly. You can use the new onmode -c block/unblock feature to suspend the engine at a consistent point (immediately following a checkpoint) while you backup the chunks. Of course this is only reasonable if you can afford to take the engine offline for the duration of the archive OR if you are using mirrors. If you are using mirrors you can suspend the engine (onmode -c block) break all the mirrors, release the engine (onmode -c unblock) and then backup the mirror drives and re-add the mirrors later. This feature was requested by another Informix customer (the name evades me now) with an innovative DBA who wanted to do it this way: o Suspend engine o Break mirrors o Add new mirrors from a third set of drives o Unblock engine o Archive the previous mirror chunk set So that the engine will continue to have mirror protection during the 'archive'. In effect he has three sets of mirror drives that he uses two at a time so that every other day he switches and backs up the previously used set of mirrors. The customer has a HUGE system that takes over a day to archive using ontape but can be done, using their system archive software, in much less time. You CAN get actual multiple mirroring using a volume manager or some hardware mirror/RAID systems to perform the mirroring instead of using Informix mirrors. This has advantages since firmware mirroring is much faster than Informix mirroring. Software mirroring tests out to be slightly faster than Informix mirroring but I have always suspected that under load Informix's intimate knowledge of the database structure may give its mirroring a slight edge over software mirroring. However, with two mirrors per drive that may no longer be true. Anyway enough for now. Art S. Kagel