Re: Direct IO

From: Dave Grantier <dave_at_foobar.com>
Date: Sat, 23 Jun 2001 01:33:00 GMT
Message-ID: <3b33f176.1305136@news.mindspring.com>

David,
Here's my two cents.
I understand direct IO to mean something to the effect of bypassing the Unix Buffer cache. Some Unix filesystems allow you to disable caching. I'm thinking of HP's JFS (by Veritas), and, of course, Veritas.
Naturally, Raw IO bypasses the whole schmeer. Cheers,

On Sat, 23 Jun 2001 00:45:38 GMT, "Dave Haas" <davidh_at_no.spam.hotmail.com> wrote:

> Hi.
>
> I have a question with regard to terminology. In several posts (and an
> argument I had with Howard a while ago :) people have used the term 'Direct
> IO'. To be perfectly honest I'm not exactly sure what that means. AFAIK
> the IO options are 1) file-system buffered and 2) Raw IO. I heard (or more
> to the point, read) a post that said something to the effect of '... direct
> I/O means that the buffer cache is not involved in the operation ...'. Does
> that have something to do with the sort-direct-write operation and the old
> SORT_WRITE_BUFFERS and SORT_WRITE_BUFFER_SIZE? I'm a little confused (as
> usual) ...
>
> Dave
>
>

Dave

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Received on Fri Jun 22 2001 - 20:33:00 CDT