Re: duplexing redos and archives

I've actually had a raid5 array melt. Early DEC arrays, before they figured out the extra fans. The plastic got soft and things went downhill from there.

The point is that a million hours MTBF does not account for the SA rewiring the cabinet next door and accidently unplugging one of the arrays -- we now mirror to different cabinets --- and assumes that they didn't plug all the power supplies into the same PDU -- as of last month's problems we wire redundant power supplies to different power distribution units -- and assumes that the air conditioning doesn't go off.

My SA's called me in one day and said RAID5 would increase performance, so I proposed some bench tests. Then I explained the difference between batch file processing and random discrete access, to explain the results of the bench tests. To their credit, they saw the point. Engineers tend to believe the authority of the sales engineers more than us mere scientists, but they will usually believe their own results.

"...Sir Gawain, Sir Lancelot and I leap out of the rabbit, thus taking the French unawares, and unarmed!"
-- Sir Bedevere, an object lesson in planning.

Peter Barnett wrote:

> Continue with your redo logs, control files and
> archive log files on raid0.
>
> We have had two complete melt downs of raid5 storage.
> The vendor said it could not happen, our storage folks
> said it could not happen. It happened! When I was
> consulting, I had a similar experience at a client
> site.
>
> The only files I will voluntarily put on raid5 are the
> data and indexes. Everything else I want on raid0 or
> 0+1.
>
> --- Joe Armstrong-Champ
> <Joseph.Armstrong-Champ_at_tufts.edu> wrote:
> > Currently we are duplexing our redo logs and archive
> > logs through
> > oracle. We do this at the oracle level because we
> > are using mirroring
> > (raid0?) and if we lose a redo log or archive file
> > the database will not
> > be affected.
> >
> > We will be moving to raid5 arrays in the future and
> > are wondering
> > whether we still need to do the duplexing. Since the
> > arrays are made up
> > of data disks plus a parity disk plus a hot swap do
> > we need to worry
> > about losing a redo log? Our sys admins are telling
> > us we don't and I
> > tend to agree with them but we want to get other
> > opinions on the
> > subject.
> >
> > How are shops handling this who are using raid5?
> >
> > Thanks.
> > Joe
> > --
> > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.com
> > --
> > Author: Joe Armstrong-Champ
> > INET: Joseph.Armstrong-Champ_at_tufts.edu
> >
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> =====
> Pete Barnett
> Lead Database Administrator
> The Regence Group
> pnbarne_at_regence.com
>
> __________________________________________________
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Don Jerman
  INET: djerman_at_dot.state.nc.us

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
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