Re: Raw I/O vs files (was Re: Raw partitions / cooked files)

> Pat Gainer writes in reply to Lee:- > In a recent append, lparsons@exlog.com (Lee Parsons) writes... > > >I think that is because you, I and everybody else already know the > >answer. The only way your are going to see a *significantly* faster > >raw benchmark is if something else somewhere is not tuned well. > > I don't necessarily think this is true. If you look at the TPC-A/B/C > benchamrks, all the leaders get their numbers using raw I/O. This implies > raw I/O can be faster when tuned. Without actually doing a huge benchmark > comparison, I would be curious to know what others have observed. > > How many DBAs are running Oracle/Informix/etc etc using raw I/O? Any? > > >Before I get flamed I should say there are cases where going raw is > >the thing to do, but those cases are rare and usually in situations > >where doing the Right thing is not an option. > > Pat Gainer I would be surprised if many Informix Online sites did not use raw I/O as the standard production environment. We certainly do. Apart from the fact that Informix advises everyone that "general" performance will be better using Raw as opposed to Cooked access. You only have to consider that if you used cooked access you are effectively doubling the file system code that you have to use to get to your data. As Online always uses it's own file system even when using cooked file space you have the overhead of the O/S code on top of the Online code. Of course in special cases cooked chunks may perform better than raw because of the additional buffering going on but with a general load I would never expect cooked to outperform raw access with Online. The question whether Online need any longer have it's own filesystem at all is seperate and I am not really in a position to comment. But my gut feel would be that a filesystem that is designed specifically for database access and which is linked directly to a database optimised buffering system will always, in the end, outperform a filesystem which is designed to do it's best for all forms of access and therefore can only be average at each. Cheers - Jim My Opinions are always my own. They may vary with time but they are all MINE -------------------------------------------------------------------- Name: Jim Gordon Internet: jgordon@ssf-sys.DHL.COM Company: DHL Systems Inc Phone: (415) 358-5911 (Work) Address: 1700 S. Amphlett Blvd. (415) 882-9728 (Home) San Mateo, CA 94402 Fax: (415) 571-6429 --------------------------------------------------------------------