Re: Log file I/O throughput

On 12 Aug 2003 20:23:12 -0700, yong321_at_yahoo.com (Yong Huang) wrote:

>Norman Dunbar <Norman.Dunbar_at_lfs.co.uk> wrote in message news:<E2F6A70FE45242488C865C3BC1245DA7040E8DC0_at_lnewton.leeds.lfs.co.uk>...
>> >> Or
>> >> to drop the mirrored copy altogether since redundancy in built into
>> >> the I/O subsystem (Hitachi S.A.N).
>>
>> Picture this, Oracle mirrors your logfiles and an operator, in a moment
>> of weakness, deletes one of the mirrored copies. The remaining mirrors
>> will not be deleted.
>>
>> Now, run the same thought experiment again, but this time with OS (or
>> SAN) mirroring, this time what happens when one of the mirrored copies
>> gets deleted - the mirrors are also deleted leaving you with nothing.
>>
>> Same applies to control files - don't let the OS mirror than unless
>> Oracle is also mirroring.
>
>Hi, Norman,
>
>I know some people don't like it. But using one log member per group
>when you have good hardware redundancy is actually good practice. It
>saves on log file single write time (when AIO is enabled). I remember
>Steve Adams recommended it (or could be somebody else?) and also
>noticed a person working at BMC on the OAUG mailing list was doing
>that. I've been doing that for some time. You just have to be a little
>more careful in deleting files.
>
>Yong Huang

Sorry to contradict you. When of the members of your hardware mirror fails, the write request to the redolog file fails, and your database will crash.
Also, when you have multiple cpus, and you did multiplex your redologs, the archiver will use both to assemble the archived redolog.

Sybrand Bakker, Senior Oracle DBA

To reply remove -verwijderdit from my e-mail address Received on Tue Aug 12 2003 - 23:26:09 CDT