Re: Q:multiple mirrors

Hi Art, everyone, Q: Say you put this third set of mirror on a dual ported storage array. After breaking the mirror, could another instance of IDS on another box with the same Informix configuration be able to use these mirrors/chunks? In article <372DC93C.52DD@bloomberg.net>, kagel@bloomberg.net wrote: > 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 > -----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own