Re: Synchronous writes & TEMP

From: VC <boston103_at_hotmail.com>
Date: Sat, 15 May 2004 10:16:25 GMT
Message-ID: <Z5mpc.51832$536.8949315@attbi_s03>

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:c84l63$5no$1_at_titan.btinternet.com...
>
>
> I believe that the writes are still buffered, even
> when they are ODSYNC writes. They still go
> into (straight through and out the either side of)
> the file system cache.

They are buffered in this sense, yes, but the write operation itself does not benefit from such buffering although reads do. The writes actually suffer from this useless buffering. In the absense of O_DSYNC, both writes and reads would perform better thanks to the filesystem cache.

>Many operating systems
> have a 'directio' (or similar) option to bypass the
> file system buffer cache.

Yes , 'direct io' would eliminate overhead due to the write useless buffering but would make read performance worse.

>
> (That's not intended to be an answer to your
> question, by the way).
>
> Maybe there's something in parameter
> filesystemio_options
> that can be used to modify the default
> behaviour.

Regards.

VC
> --
> Regards
>
> Jonathan Lewis
>
>
Received on Sat May 15 2004 - 05:16:25 CDT