Re: Informix 7.X and RAID 5

> I have some confusing info indicating that RAID 5 is not > suggested/supported > in 7.X? > > Anyone have some insights? RAID devices appear as normal Unix disks and Online doesn't notice the difference so therefore you could say they are supported. They are not suggested for Online 7 because this version allows you to manage your data with much finer granularity. Not only can you manage the placement of your tables and individual indexes but you can also manage fragments which at one extreme can be as small as a row or an individual index key. One advantage of fragmentation is that Online uses this for PDQ resulting in significant performance improvements for queries. On the other hand, if you have a database in the terabyte region, managing these fragments would be impossible so you would use RAID or Logical Volume Managers to help you distribute the I/O load and basically forget fragmentation. You lose the PDQ facility but you gain redundancy, hot-pull, and to some extent, dynamic volume management. What about fragmentation on top of RAID? I don't really know. I suspect this will result in poor performance due to excessive head movement but I wouldn't be surprised if it was faster. I'm looking forward to Joe Lumbley's RAID test results. (How are the tests coming along Joe?) Personally, I would rather have PDQ and pay someone else to do DBA. > Rb. David W Chan Objective Research Ltd dwc@cix.compulink.co.uk