Re: Multiplexing Datafiles?

"Rob Jolliffe" <rjolliffe_at_my-deja.com> wrote in message news:8n4295$mqp$1_at_nnrp1.deja.com...
> Hi,
>
> I'm just beginning to learn Oracle, and I was reviewing some Email
> regarding Raid5 vs Raid0 performance. It seems Raid 0 is significantly
> better for performance - but you lose the redundancy of Raid 5 (or even
> Raid 1).
>
> I was trying to also determine if in a data tablespace it is possible to
> multiplex (mirror) datafiles the same way you can with a Redo log group.
> I was totally unable to determine if you are or are not.
>

Absolutely not. Never has been, and there never will be -because it is entirely pointless. The reason for duplexing your data files is, presumably, to avoid complete disaster in the event that one of them dies, gets deleted, corrupted etc. That is precisely what the Redo Logs are there for. Provided you've kept all your redo since the time of the last backup, you can reconstruct any given data file up to the precise time of failure.

So if you're mirroring your Redo, you have provided all the protection your data files ever need.

(Conceivably, you can use external, hardware mirroring of data files to enable recovery to take place *faster* -you just break the mirror and use the good copy. No need to wait for all that Redo to be re-played. But that's a mean-time-to-recovery issue. It's certainly not necessary).

> Can anyone tell me? I know you can stripe tablespaces - but can you
> mirror them? Perhaps this requires creating two tablespaces and somehow
> matching them?
>

Forget it. There's no such concept in Oracle, because the Redo does all the protection work we need.

Regards
HJR
> Thanks very much
>
> -Rob
>
>
> =============
> From the desk of Rob Jolliffe
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Sun Aug 13 2000 - 00:00:00 CDT