Re: Totally NEwbie Question

"Jim Kennedy" <kennedy-family_at_home.com> wrote

> A raw device is one that does not have a file system on it. In the windows
> world it would be partitioned but not formatted. Thus the entire device is
> treated as if it were a single file by Oracle. While you can get better
> performance out of a raw device, better IO that is. Raw devices can be more
> administration.

To add another cent to this.

I/O performance increase is very small, unless you are dealing with a kernel and/or file system that is not as "efficient" as it could be (not a very good argument these days as we are working with fairly mature operating systems where kernel file i/o is not a real performance issue).

IMO, one of the last reasons that you should choose a raw device over a file system (or cooked device) is I/O performance. If I/O is that critical that you need to resort to raw devices, then you have a big problem. One that can be better solved address the hardware issues than to attempt to squeeze the last few drops of performance by using raw instead of cooked devices.

As for administration, IMO raw devices is actually LESS administration. It is more bit more complex - but only because sys admins and DBAs very seldom deal with raw devices and need to RTFM a bit. However this does not necessarily equate to more administration. Raw devices IMO requires _less_ "maintenance" from the sys admin side than a cooked devices.

So why use raw devices? Besides the debatable issue about i/o performance, you need to use it on (certain?) clusters. Not familiar with NT clusters, but on the Unix clusters - we used Pyramid MPP - you have to use raw devices to run Oracle Parallel Server.

--
Billy