Re: RAID 5 or 5 hard disks?

Barbara Kennedy wrote:
>
> My experience has been that Raid 5 gives you a large performance hit. It
> may be true that if you have enough disks for raid 5 then it is okay. But
> people who tend to use raid 5 (not all) are looking at the bottom line in
> terms of raw cost and not in terms of the cost of poor performance. Thus
> they tend to buy the minimum (e.g. 3 disks) and not more (like 10).
> Jim
>
> "Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk> wrote in message
> news:90qba0$3n$1_at_soap.pipex.net...
> > Hi
> >
> > Raid 5 is fine (so long as you have sufficient disks). However redo and
> > archive logs should always be mirrored. This suggests that you should have
> > as well as the raid 5 volume at least one mirrored pair for logs and
> > preferably at least 2. You can then put the os on one mirrored pair the
 logs
> > on another and the data on your raid5 set.
> >
> > You will always get better performance from striped and mirrored disks but
> > this tends to be expensive compared to raid5.
> >
> >
> > --
> > Niall Litchfield
> > Oracle DBA
> > Audit Commission UK
> > "Allen" <allenh_at_starbase.neosoft.com> wrote in message
> > news:BD71F762829CE2EA.D22E5AC688FEA19C.C4951E8FAF1A6749_at_lp.airnews.net...
> > >
> > > I've always installed my databases with indexes on one HD, RBS on
 another,
> > > etc.. now I'm in a new environment where they want to use a Raid 5 disk
> > > box that will have all my datafiles in the same volume. Supposedly the
> > > RAID stuff will take care of spreading out the files on different HDs.
> > > Is this cool, or should I still insist on several different HDs within
 the
> > > Raid 5 environment?
> > >
> > > thx.. Allen
> >
> >

Agreed - typically the raid-5 installations that work well under heavy load have a massive cache - and of course end up costing just as much as the RAID-0/1/etc solution would have done... :-)

-- 
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Connor McDonald
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"Some days you're the pigeon, some days you're the statue"