Re: Direct IO

Steve Adams has done some research on this: "Oracle on NT always explicitly does direct I/O. The datafiles are created with FILE_FLAG_NO_BUFFERING and opened with IRP_NOCACHE." It's easy to mistakenly extrapolate that to mean that NT never does buffering. Note that he only says Oracle on NT, not NT in general. And he seems to say even the Microsoft people think the NT porters of Oracle are doing a bad job in choosing direct I/O on NT since direct I/O on NT disables fast I/O. So don't think direct I/O is always faster.

There's an O'Reily book on NT File Systems Internals, but I spent at most 5 hours reading it. If you think you know OS well enough, you may take a look and educate us here.

Yong Huang
yong321_at_yahoo.com

"Dave Haas" <davidh_at_no.spam.hotmail.com> wrote in message news:<jdPZ6.80657$Jg4.8474809_at_news1.telusplanet.net>...
>
> In terms of the NT Direct IO thing. If it is on by default, does that then
> mean that all operations on an NTFS device bypass the cache? That seems a
> little wierd as NT likes to tout itself as a fileserver OS (with a fair
> amount of physical memory being dedicated to file ops IIRC).
>
> Cheers,
>
> Dave
Received on Mon Jun 25 2001 - 23:27:55 CDT