Directio question

Hi,

My name is Stefan P., Im working on http://www.systemdatarecorder.org
and I have started to test and consider replacing for our solution
apache over nginx. Im getting to know nginx and I like the server.

Some question reading over http://wiki.nginx.org/NginxHttpCoreModule
about DirectIO:

“The directive enables use of flags O_DIRECT (FreeBSD, Linux),
F_NOCACHE (Mac OS X) or directio() function (Solaris) for reading
files with size greater than specified. This directive disables
use of sendfile for this request.”

DirectIO in Solaris is a feature, when enabled lets you to bypass
entirely the
OS’s page cache and read/write directly from/to disk. This has some
benefits where workloads are database servers and you want to avoid
double caching.

Im a bit curious under what situations would like to have DirectIO
enabled on
nginx and are we talking about same thing when we refer to directio ?
http://www.solarisinternals.com/wiki/index.php/Direct_I/O

Usually most applications will benefit of having the OS’s page cache
involved
rather of going to disk.

Thanks,
stefan

On Sun, Mar 07, 2010 at 08:07:13PM +0200, Stefan P. wrote:

F_NOCACHE (Mac OS X) or directio() function (Solaris) for reading
http://www.solarisinternals.com/wiki/index.php/Direct_I/O

Usually most applications will benefit of having the OS’s page cache involved
rather of going to disk.

Yes, nginx’s directio is what you have said. It may or may not improve
perfomance of serving large files when a server physical memory is much
less than summary size of the files.


Igor S.
http://sysoev.ru/en/

Yes, nginx’s directio is what you have said. It may or may not improve
perfomance of serving large files when a server physical memory is much
less than summary size of the files.

aha, cool. Many thanks for clarification.

stefan

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