RE: KAIO

Thanks. In the past I remember seeing recommendations against using cooked simply because it was not considered 'safe'. The argument was something along the lines of needing to be sure that data was actually written to disk rather than stuck in the cache when a system failure occurs. I never took much notice of the argument of course, I have always use raw. -----Original Message----- From: Martin Fuerderer [mailto:MARTINFU@de.ibm.com] Sent: Monday, January 24, 2005 7:05 AM To: mark@vuntec.com Cc: informix-list@iiug.org; owner-informix-list@iiug.org Subject: 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