Re: Combining Data Guard with clustered redo logs for high performance standby

Dennis G Allard wrote:
> Hello everyone.
>
> In Data Guard, setting LogXptMode = SYNC incurs
> a performance penalty on the primary database.
>

You mean Data Guard Broker, not Data Guard.

> That is because there is latency involved in
> writing to the standby redo log.
>
> It should be possible to use an active/passive
> cluster solution whereby the redo logs are kept
> on an external storage array. When the primary
> system fails, the standby would take over the
> primary server's redo logs by mounting the redo
> log disk partition.

You are confusing online redo logs, standby redo logs, and archived redo logs.

>
> I realize that one can use RAC to achieve HA
> via a clustered disk array. However, me thinks
> that a less expensive solution for HA could be
> obtained by combining Data Guard with the above
> idea of using external storage just to store the
> redo logs (and control files?). In this way, one
> should be able to operate Data Guard with a
> LogXptMode set to ARCH. At time of fail over,
> one would need to point the Standby database
> server to the redo logs that had been previously
> mounted by the primary server.

Are you willing for your online redo logs to be a single point of failure, or not? Once you answer that question, you can proceed.

>
> I have not yet combed the Data Guard documentation
> to attempt to figure out if I can make use of its
> facilities for transferring archive redo logs and
> initiating fail over yet somehow inform the standby
> to mount the redo logs on the external storage
> prior to activation.
>
> Has someone out there attempted this feat?
>
> Thanks,
> Dennis

-Mark Bole Received on Mon Aug 15 2005 - 20:56:56 CDT