Re: OFA Architecture with RAID

If you *only* had one disk subsystem - a RAID5 array - then you would *achieve* nothing in terms of performance by using multiple mount points. I'd definately put Oracle (i.e. the binaries) in it's own mount point (filesystem), but that's just for installation, maintenance and upgrade issues. I'd put the db in one mount point spread over multiple directories.

As regards performance measurement in the disk I/O subsystem, you'd only get true metrics from montioring the I/O rates of the RAID array (from OS tools outside of Oracle), and Oracle I/O metrics from looking at the SGA stats which will give you I/O per datafile values. If the RAID5 array struggles, it struggles, so you are either going to have to live with it or split it up anyway...

As regards the *type* of I/O when you do decide you have to split it, that's pretty easy with a knowledge of Oralce and a general knowledge of your application and the types of operations performed by it. I'd think the *volume* of I/O per datafile would be of far more use when deciding what to split where than just the type of I/O. And once you've decided the RAID5 on it's own is no good and you've split it up, well then you can start doing some more intensive I/O monitoring/balancing.

Leaving the whole lot on one drive also makes it much easier to backup/restore, which may be useful if this is someone's first Oracle outing...

The only reason I can see for creating multiple mount points was if you were planning to eventually move off the RAID5 array (or partially move off it) and didn't want to get invloved in having to rename your oracle datafiles, but this is a fairly simple task anyway.

Still, I really wouldn't go this route at all if I even suspected that I might become I/O bound - anywhere - with my Oracle db on a RAID5 system. Better to save yourself sometime and start with separate, multiple drives in the first place, I'm sure we'd both agree.

Steve Phelan

(Oracle 7 & 8 OCP)

"Christopher M. Day" wrote:

> Steve,
>
> I would disagree, you've just bundled the physical and logical
> performance metrics together - how would anyone be able to substantiate
> additional components in the disk subsystem ?
>
> If you are forced to compromise on the disk subsystem physically, then
> you can help yourself by making the correct logical drive mappings.
>
> Chris.
> (It makes it a lot easier to diagnose random r/w and sequential r/w)
>
> Steve Phelan wrote:
> >
> > No, you really only need one mount point, as the RAID devce will pull *all* the
> > mount points onto one disk set anyway (as long as you created them all on the
> > same RAID 5 set). If my whole system was on a RAID5 array (which may be a bad
> > idea, but let's avoid that issue here) then you only have one file system mount
> > point. Just create multiple directories on it to hold separate copies of things
> > like redo mirror and control files, so you don't loose the lot if some hits
> > delete in the a bad directory.
> >
> > Steve Phelan
> >
> > (Oracle 7 & 8 OCP)
> >
> > gremlin wrote:
> >
> > > Do you still need multiple (4?) mount points if your file system is on a
> > > raid? Doesn't that take care of the thing you are trying to prevent
> > > automatically?
> > >
> > > Mike
> > >
> > > Steve Phelan wrote:
> > >
> > > > OFA deals with having enough mount points to save you from a single drive
> > > > failure. It doesn't include any RAID (or non-RAID) fault tolerant
> > > > features. In other words, you don't have to follow OFA to the letter as
> > > > you can build in some of it's features using your hardware.
> > > >
> > > > As regards which bits to put where, you'll really have to look at the
> > > > uptime/recover-time you want plus the read/write performance of each part
> > > > of your database you expect. None of this can be answered without a very
> > > > good knowledge of your system.
> > > >
> > > > Read up on Oracle before you jump in on this, and get some consultancy.
> > > >
> > > > Steve Phelan
> > > >
> > > > (Oracle 7 & 8 OCP)
> > > >
> > > > Scott Patterson wrote:
> > > >
> > > > > I was wondering if anyone out there had any insights or suggestions on
> > > > > how to configure a 7 disk compaq box running windows nt and Oracle
> > > > > 8.05. I have read about the OFA architecture and wish to be compliant
> > > > > along those parameters, but I am a bit confused how to also take
> > > > > advantage of RAID technologies as well. I will have the ability to mix
> > > > > and match different RAID levels along the 7 drives, however Im not
> > > > > sure what OFA tablespaces should be say RAID1 and which should be
> > > > > RAID5 or whatever other RAID levels should be considered. I generally
> > > > > will be following the default tablespace schemas of the OFA
> > > > > architecture.
> > > > >
> > > > > I would appreciate any insights on this subject,
> > > > >
> > > > > thanks Scott
> > >
> > > --
> > > -----------------------------------------------------
> > > To reply to me via email, remove the "__NO_SPAM__" in
> > > the header email address.
> > > -----------------------------------------------------
Received on Thu Feb 25 1999 - 15:29:22 CST