Re: Redo log & RAID

From: Paul Drake <paled_at_home.com>
Date: Sat, 14 Apr 2001 02:01:00 GMT
Message-ID: <3AD7AF96.7E563163@home.com>

default wrote:

> My question then becomes, if you are mirroring with the
> software why mirror with the hardware? Wouldn't that become more
> troublesome. Why do both if one is sufficient and even better? Or is it?

Hardware mirroring protects against a hardware failure. If both drives are on the same RAID controller, and the controller calls it quits, you have no logfile.
If there is a writefile() error to the redo log, you have no logfile, and the instance terminates.
If you have multiple log members on independent drives and independent controllers, you have eliminated the single point of physical and logical failure.

The scariest message I have ever seen on an Oracle box is

BOOT DEVICE NOT FOUND. Don't depend on a single RAID controller. Writefile() errors do happen. Be prepared.

hth,

Paul Received on Fri Apr 13 2001 - 21:01:00 CDT