Re: Best RAID configuration.

IMHO this is not good advice, one redo log per disk is wasting disks...writes to logs are sequential and different logs are never written to at the same time so the extra spindles could be used elsewhere. One raid 0/1 set for all logs is quite sufficient. Do not put two members from the same group on the same disk though. As for 0/1 for tablespaces, this is highly suspect, but I am assuming that the tablespaces are read more than written to in which case RAID 5 is more suitable, if on the other hand you have an update intensive database then 0/1 would be better. Do not configure you I/O as per the size of the database, this rule of thumb will land you in trouble. Configure your disks as per your application demands, put hot files/tables on separate raid sets and keep indexes away from data. Keep rollbacks away from data and keep redo logs on their own disks. Shop around for smaller disks, they are quite cheap now, give me 12x 4.5 GB disks over 6x9GB over 3x18GB disks any day. Big disks are making my life as a DBA a real p.i.t.a. Databases need spindles and not MB/GB capacity.

"Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message news:3944EFC4.5285_at_yahoo.com...
> Tony Longhurst wrote:
> >
> > We have a large Oracle 7.3 based database, running under NT 4, that has
 a
> > requirement for approximately 50 GB worth of system files and
 dynamically
> > changing tablespaces on one logical drive and upto 300 GB of read only
> > tablespaces that are contained on a separate logical drive.
> >
> > I am considering a RAID of 0 + 1 for the system files and dynamically
> > changing table spaces and RAID 5 for the static tablespaces.
> >
> > This would result in 6 x 18 GB drives for RAID 0 + 1 and 7 x 50 GB
 drives
> > for RAID 5.
> >
> > My question is whether have just 3 drives for the striping, prior to
> > mirroring, is enough. Would it be much better to have 14 x 50 GB RAID 0
 + 1,
> > for example, although this would be a lot more expensive. Another option
> > would be to use 10 x 18 GB drives although we do not strictly need the
> > capacity, would this increase the performance. This system has a heavy
> > usage.
> >
> > Any advice gratefully received.
> >
> > Tony
>
> I've always found that pretty much any system that choose disks based on
> the SIZE of the database end up suffering...Plan around the config that
> will perform and scale well - no matter how much "free" space you end up
> with...IMHO this typically means at the barest possible minimum
>
> - a disk per redo log (2 if mirrored)
> - archives separate
> - 0+1 stripes for tspaces
>
> and then for medium sized db's, start looking at
>
> - temp tspaces on separate stripes
> - one rollback segment per disk
>
> and I forgot...a big chequebook.
>
> HTH
>
> --
> ===========================================
> Connor McDonald
> http://www.oracledba.co.uk
>
> We are born naked, wet and hungry...then things get worse
Received on Mon Jun 12 2000 - 00:00:00 CDT