Good philosophy. But I've seen it practiced where it makes no sense.
Someone must have told the DBA(s) who set up one of the databases I
inherited that you should always duplex your redo logs. Great. so they
did.
Of course, the disk farm is one mount point, a NetApp filer, so the
duplexed logs are not only on the same set of disks, but these guys
created them in the SAME DIRECTORY.
makes loads of sense, right?
sigh....
- "Fink, Dan" <Dan.Fink_at_mdx.com> wrote:
> This may be 'old school' thinking, but I prefer to duplex my redo
> logs. Why?
> Because there are some things that mirroring cannot protect you
> against.
> 1. The deletion of a redo log through human error (been there,
> recovered
> from it...)
> 2. The logical corruption of a redo log (never experienced it myself,
> but it
> is theortically possible)
> 3. Oracle's fault tolerance regarding the ability to function as long
> as 1
> redo log in a group is accessible
>
> Considering the critical nature of the redo logs (lose one and your
> recovery
> is done...and perhaps your job) and their small size in relation to
> overall
> databse size, duplexing in a group makes sense.
>
> This is one of those issues where valid arguements exist on both
> sides. In
> some ways, the logical arguements are on the side of not duplexing
> redo logs
> that are mirrored. However, when you consider that the loss or
> corruption of
> a single redo log can cause the database to be unrecoverable is
> enough to
> justify the cost of duplexing.
>
> Just my humble (old school) opinion
>
> Dan Fink
>
> -----Original Message-----
> Sent: Tuesday, August 06, 2002 12:13 PM
> To: Multiple recipients of list ORACLE-L
>
>
> 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
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> Author: Joe Armstrong-Champ
> INET: Joseph.Armstrong-Champ_at_tufts.edu
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Received on Tue Aug 06 2002 - 16:13:42 CDT
