RE: KAIO

Hi, I'm not sure. I happen to know this for Linux, but for other OSs I don't really know. I think it is always said that on Solaris you should use raw devices (rather than cooked files) for better performance, but it's been a long time that I had a look at the difference myself. For others (e.g. AIX, HP-UX) I just don't know. Regards, Martin -- Martin Fuerderer IBM Informix Development Munich, Germany Information Management owner-informix-list@iiug.org wrote on 22.01.2005 03:18:56: > Are there any other OS's where the FS caching mechanism is very > efficient and therefore should be taken advantage of when memory is not > an object? > > -----Original Message----- > From: owner-informix-list@iiug.org [mailto:owner-informix-list@iiug.org] > On Behalf Of Martin Fuerderer > Sent: Friday, January 21, 2005 3:57 AM > To: Markus Bschorer > Cc: informix-list@iiug.org; owner-informix-list@iiug.org > Subject: Re: KAIO > > Hi, > > a) there's no KAIO support in 9.40.x (as others have already noted). > You can use raw devices, but not KAIO. > > b) KAIO will be supported with the next version. This is what the > Beta-Tester most probably was talking about. > > c) To judge the effect/benefit of KAIO on Linux is quite difficult > and depends heavily on the situation/circumstances of the > system: > > - if you have a lot of spare memory on your system (i.e. that > you do not need for BUFFERS in the server and that is not > used by anyone else, that Linux will use that memory for > file system caching. And this is known to be very effective. > > For a system like this, KAIO will not have much benefit, as > filesystem I/O is very efficiently done via Linux's file system > caching. > > - if you have a system that uses all the (physically) available > memory for applications (most prominently IDS), then Linux > will have very little memory for file system caching. That will > significantly slow down file system I/O. > > This is a system where KAIO will provide the most benefit, > and this benefit will normally be perceived as significant. > > The notion that "KAIO is a magic bullet" is to be judged on the > background, that the general assumption is IDS will be > configured to use as much memory (BUFFERS) as possible. > And, not to forget, on other UNIX flavours, where the file system > caching is not as efficient as on Linux, KAIO always had a huge > performance benefit. > > TIA, > Martin > -- > Martin Fuerderer > IBM Informix Development Munich, Germany > Information Management > > owner-informix-list@iiug.org wrote on 20.01.2005 15:04:48: > > > Hi all, > > > > on some websites, you can read wonderful things concerning KAIO, like > > dramatically better performance in high-traffic-scenarios. > > Linux Kernel 2.6 supports KAIO. I talked to a Beta-Tester of IDS > Version > 9.4 > > UC5, which supports KAIO under Linux 2.6. He told me, that there is no > > appreciable performance-benefit when using KAIO. > > > > Does anyone know, whether that's because of a bad > informix-implenattaion > of > > KAIO, or a of bad linux-implementation of KAIO? > > Is KAIO really such a magic bullet? > > > > Thanks in advance! > > > > Bye Markus > > > > > > sending to informix-list > > sending to informix-list sending to informix-list