RE: KAIO

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