Re: Online V7 and Parallel Queries

Jeremy Russell wrote: > > Is it true that PDQ, parallel queries in OnLine V7.x will use both > primary chunks and mirror chunks to retrieve data concurrently when > performing a query expected to return large volumes of data??? > > The reason for asking - trying to determine whether software mirroring > has advantages over hardware mirroring, in terms of overall speeds. I > thought that hardware mirroring is faster than letting Informix handle > the mirror processing - if however, the mirror chunk is also read, > then maybe the software approach is best. I also hear that mirror chunks would be read in version 7.2, but I have not confirmed this. However, I believe the best route is still to use hardware mirroring for performance, and use fragmentation for your PDQ strategy. By selecting an appropriate fragmentation strategy for your data distribution and use, you can dictate exactly which chunks, and therefore which disks, are read during queries. You can also decide whether to 'skip' over chunks which are down with DATASKIP. That is only my 2c worth, and that's South African cents. :-( Cheers, -- Mark. +-------------------------------------------------------------------------+ |Mark D. Stock - The West Solutions Group http://www.west.co.za | | The Informix FAQ is at http://www.iiug.org | |mailto:marks@west.co.za +------------------------------------------------+ |Tel: +27 11 803 2151 |If it doesn't work... force it! | |Fax: +27 11 803 2189 |If it breaks... it needed replacing anyway! | |Cell: +27 83 250 2325 |Well, that's how I code anyway! | +------------------------+------------------------------------------------+