Re: RAID 0+1 and recommended stripe size

Bricklen wrote:
>
> Thanks Connor, for the confirmation, and to Joel as well for the SAME
> article.
> I will definitely try the suggestions I've received and benchmark for
> our system.
>
> btw, I notice in that SAME article that Joel has provided:
>
> http://otn.oracle.com/deploy/availability/pdf/oow2000_same.pdf
>
> that Juan Loaiza et al. suggests using 1 meg stripes, as well as a 1 meg
> db_file_multiblock_read_count, and OS IO size limits to 1 meg.
>
> I'm wondering if anyone has tried both methods and has an informed
> opinion on which is _generally_ more performant? Mind you, I'm not
> after some magical incantation like fast=true, just a push in the right
> direction to start off my testing/benchmarking.
>
> My reasoning: I'm pressed for time on this issue so the option to try
> every possible way is out of the question.
>
> Thanks again everyone for the suggestions!
>
> Cheers,
>
> Bricklen
>
> Connor McDonald wrote:
> > The general consensus around the place is:
> >
> > block size * multiblock read * n
> >
> > where n = 1, 2, 3, ... etc
> >
> > Which 'n' is best? For *your* system it could be any of them, if you
> > can run some benchmarks you'll find the best for your system. It might
> > match the thoughts out there in the public forums, it might not...But
> > you will at least know thats its the best for *your* system
> >
> > hth
> > connor
> > --
> > =========================
> > Connor McDonald
> > http://www.oracledba.co.uk
> >
> > "Some days you're the pigeon, some days you're the statue"

That's why I suggested playing around. I've seen 1m stripes work very well with Solaris where the OS max io was set to 1m (which btw required some special tweaking of the file system config to get it to work - a default ufs/vxfs file system only allowed 256k). But as well, because full scans then looked so attractive to the optimizer we had to tweak the optimizer_... parms to balance things a bit...

We ended up with whizz-bang IO performance, but this is quite different to the advocates of SAME which claims that "you simply set everything to 1m and voila!"

hth
connor

-- 
=========================
Connor McDonald
http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue"