Re: Mirrored disks Vs duplexed logs

Steven_Dodsworth_at_qsp.co.uk (Steve Dodsworth] wrote:

>Hello world,
 

>This seems a daft question, but here goes.
 

>Oracle recommends having duplexed redo logs in case of disk failure. I read
>that to be similar to mirroring. If a database resides on a system that has
>disk mirroring, do the redo logs still have to be duplexed - I cannot think of
>a reason to still have more than one 'database defined' copy. Does any one
>know of any reason to keep two 'database configured' copies.

Steve,

Why not duplex the discs instead of mirroring them. That way your disc controller is protected as well. These days, it is so rare that discs fail that I feel that just as much effort should be put into duplicating far more of your machine than just your discs.

That's not to say that discs don't fail... but five years supporting 82 sites with an average of 5 discs on each site led to about half a dozen failures (interestingly, it looked like the arrival of a 'sell by' date, as they all failed quite close together! ). If you can physically separate the discs and provide separate power supplies to them, then that is even better!

Steve Received on Wed Jul 03 1996 - 00:00:00 CEST