Re: SAME methodology questions...

"Ana C. Dent" <anacedent_at_hotmail.com> wrote in message news:<xIHEa.65564$MJ5.19024_at_fed1read03>...
> Burton Peltier wrote:
> > I have no experience, but I am also curious about how others are doing this
> > after recently reading about this because there are more people (in our
> > company) recommending SAME.
> >
> > Sorry if I am creating a discussion you didn't want, but I would like to
> > also hear from those who use SAME to explain a couple of things about their
> > setup.
> >
> > SAME is suppose to "keep it simple" . It seems it does IF you configure the
> > disks correctly, but the 1 thing I would still worry about is not
> > multiplexing REDO to 2 different sets of disk spindles. Does anyone using
> > SAME have a good explaination why this is not potentially a problem.
> >
> > Also, there are a couple of little details like the 1M stripe size and
> > "using the outer edges of the disk platter for frequently accessed files" ,
> > that are not so simple. Our SysAdmin didn't have any idea how to do the
> > outer edges setup on Sun A1000 arrays. Does SAME require specific/expensive
> > hardware?
> >
>
> SAME does "keep it simple", but at what price?
>
> WRT the 1MB stripe size...
> I state categorically that I've NEVER seen Oracle
> ask for or get anything close to 1MB in a single I/O
> request/operation.

I'm not saying SAME is always a good price, but the win (or wash) comes from a series of I/O's that happen to already be buffered, one way or another. Worrying about single I/O requests misses the point of SAME, which is that it is not cost-effective to worry about them.

>
> What is the product of the Oracle block size times
> Oracle multiblock read count?
> Isn't this value the largest I/O request by Oracle?
>
> What problem are you really trying to solve?
> What are the metrics & their values which will
> confirm that you've really achieved the desired goal(s)?

Those are the correct questions to ask. SAME, of course, says it is not cost-effective to worry too much about them. I think that my be valid for sites with very similar hardware to that in the paper, and there may be many of them. It is not OK for large or serious or every-disk-revolution-is-critical shops. I think SAME won't be valid over generations (with a generation being less than 2 years), and perhaps goes too far in generalizing which requirements it can cover.

jg

--
@home.com is bogus.
Think LUN=disk for the purposes of OFA.