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peacocda_at_yahoo.com (Dan Peacock) wrote in message news:<67044b3b.0112051400.524933c9_at_posting.google.com>...
> I'm going to disagree with your assertion.
I'm going to disagree with your, so it's OK. :-)
> If you have only a few
> data files, you cannot take advantage of parallel query without a
> striped set of some kind as you will bottleneck on a single spindle
> and have idle processes that are doing nothing but waiting. Now, I
> used to be a RAID5 is great always zealot. I've since modified that
> stance, but I will say this: most applications are read intensive, and
> it's a documented fact that RAID5 sets are very good at reading data
> off the disk.
Maybe I'm wrong, but I think that you can have as much of datafiles as
you need. So If you want to take advantage of PQ, then you can have
tablespace with ten datafiles across ten disks.
If you're using RAID1 you can use PQ, because you already have your
data on two disk and can read from them in parallel.
The problem with RAID5 is that your files are not spread according to
your needs, but by internal mechanism. So is hard to tune your I/O
access by spreading across the disks, because you never know where
your files are.
The worst scenario is to use one RAID5 set for all datafiles, that's
very bad and I've seen it for many times.
The biggest advantage of RAID5 is the price for it. RAID1 is more
expensive because of disk prices and even more because of disk slot
prices. So If you have only few disk bays and can't afford bigger
server or external storage, then using RAID5 for some large tablespace
is definitely a good option. Just do not use RAID5 for redologs and
temp and do not put your index tablespace on the same RAID5 set as the
data tablespace, because you can realize that your indexes will be on
the same disk with appropriate data, because Murphy´s laws are
working. :-)
-- _________________________________________ Dusan Bolek, Ing. Oracle team leader Note: pagesflames_at_usa.net has been cancelled due to changes (maybe we can call it an overture to bankruptcy) on that server. I'm still using this email to prevent SPAM. Maybe one day I will change it and have a proper mail even for news, but right now I can be reached by this email.Received on Thu Dec 06 2001 - 02:35:59 CST