Re: DataGuard9i vs Array Based Mirror

You have good questions and ideas here. I currently use Data Guard for a 24x7 system that requires no down time. The Setup I've got is an HA cluster with a remote site(a third server) containing the standby. Currently, I use Instant Protection mode, this is one step below Guaranteed. One thing that Guaranteed Protection requires is a StandBy instance always be available. Well, if you're going to use the standby for performing your backups, then when you shut it down for a cold backup, your primary instance is stopped. The reason why in the mode you specified, well, because of the mode, it requires at least 1 standby be available at all times. That's why I use Instant Protection, because then after a backup, I perform approx. 3 log switches to get Oracle to re-transmit the logs I missed during the backup of Standby Instance.

Now, in the event of a total site failure, yes, you would actually perform the failover steps to activate the standby to be the primary db now. And yes, you'll have to restore a current copy of the primary instance(which is normally the standby site) over to the Primary Site(which would then be the standby instance). Once both sites are sync'd up, you then may perform the switch over back to the primary site. So, yeah you'll be spinning tapes and performing standby recovery on the primary site, but, you have to do that anyway in the event of a site failover. Plus, you still have to re-image the primary db in order to setup the configuration anyway. So, in the event of a failure, you'll have some exposure, but, the degree of exposure will have to be looked at. i.e. what's the chances of two sites, as long as they are geographically separated, encountering a total site failure at the same time. I'm guessing that you'd still mirror or protect your filesystems on both sites either with Raid 5 or mirroring, plus protecting your server hardware wise in some manner.

HTH,
Pete's

The views expressed here are solely my own and not that of my employer.

"jamest" <jamest_at_earthlink.net> wrote in message news:<Lmdpa.37095$4P1.3343062_at_newsread2.prod.itd.earthlink.net>...
> Hi,
>
> We're trying to establish where the decision points are in picking a
> remote standby solution for a big Oracle installation that must have zero
> data loss between sites. The solutions in consideration are a
> physical standby DataGuard9i DB in "Maximum protection mode" vs.
> Disk Array based remote mirroring over a SAN (continuous access
> on EVA or XP arrays)
>
> As far as which solution would get the prize for day to day
> (synchronous IO) performance we still need to run some tests.
>
> My initial feel is that DataGuard is much less expensive but would be a
> slower
> recovery in the event of a catastrophic disk failure.
>
> Am I wrong ? Below are the points I considered. Please correct me
> and/or let me know what else I should be taking into consideration.
>
> Thanks,
>
> jamest_at_onemain.com
>
>
Received on Wed Apr 23 2003 - 11:39:38 CDT