Re: Remote Storage Mirroring vs Dataguard - Important

Date: Wed, 6 May 2015 11:23:29 -0400
Message-ID: <>

Yes. Generally, this can be a *big* plus. The licenses needed to operate a standby database can cost hundreds of thousands of dollars. This is probably the only reason I would consider storage-level replication for DR. (It can be used for all sorts of other clever purposes elsewhere, though.)

Of course, the need to restore/install Oracle software, and maybe configure some devices (e.g., if using ASM) could make your failover a little-less-than-instantaneous.

Personally, I have higher confidence in a dataguard standby -- if for no other reason that I know it is ready for failover at a moment's notice, and I can validate the integrity of the database as often as if I choose to. But sometimes there are compelling reasons to sacrifice a little confidence.

On Wed, May 6, 2015 at 10:50 AM, Mladen Gogala <> wrote:

> On the other hand, you can do storage replication, without consuming an
> Oracle license. Essentially, you can just replicate your storage and, if
> switchover is needed, restore the Oracle software from backup, bring up the
> instance and go on. Saving on Oracle licenses is a BIG plus.
> On 05/05/2015 02:22 AM, Svetoslav Gyurov wrote:
> Hi Sanjay,
> I used storage replication many times to copy prod to dev or take a
> snapshot before some major activity but never used it in a way as a DR.
> To answer your questions:
> - I would prefer DG because it's much more flexiable. You've got an idea
> what is the transport lag, apply lag and what is the state of your standby.
> You can open the standby as readonly, ADG or ever snapshoot standby to do
> some testing. Switchover is just a matter of one command through the
> broker. I cannot see neither of these happening with the storage
> replication.
> - It should be fine, as long as you replicate all the ASM LUNs. If you
> open the standby database you'll always have to do instance recovery, keep
> that in mind.
> - Yes, you can have your storage replication in SYNC. Pretty much it's
> similar to DG - the blocks from the first storage arre written to the cache
> of the second storage and they an acknoledgement is sent.
> - Not sure what the question is but if you have a GAP the storage systems
> are smart enough - and because we are only replicating blocks they can
> assisiliy recover the gap and become in sync again.
> - The fastest and safe way to bring the standby database in consistent
> state is by using DataGuard broker.
> - Modern storages have the option to change the direction of the
> replication so this shouldn't be a problem.
> Regards,
> Sve
> On Sat, May 2, 2015 at 4:19 AM, Sanjay Mishra <
> > wrote:
>> Can anyone share their views on the following on Real practical
>> experience with the setup in their environment. I had worked with dataguard
>> but never with Storage Replication for Disaster recover.
>> Some points for the required environment which can affect or help in
>> providing or sharing the experience
>> - Oracle 11g 2-Node RAC setup using ASM on both Primary and DR site
>> - Database size range from 1-5Tb
>> - Database has lots of DML activites on daily basis
>> Questions:
>> - What is the best option to be used for Disaster Recovery when has
>> to choose Storage Replication vs DataGuard for RAC setup and if can provide
>> why you think one preferred over other as per your experience ?
>> - Does there can be issue if Primary storage or server crashed and
>> Recovery either failed to start the Datbase on DR or lost some data ?
>> Keeping in mind that we are working in SYnc Mode.
>> - Is Storage mirroring can be setup so that both Primary and Remote
>> storage is almost SYNC like Synchronous Data Giuard Setting ?
>> - Is it possible that we may loose the DR location and Storage
>> Replicated environment failed to start ?
>> - Which one is faster to bring Database live, Storage mirrored DR env
>> or Dataguard based environment?
>> - How to go back or switch back to original Primary when you have
>> done switchover initially to DR location ? In Oracle Dataguard we can go
>> back using Flashback DB feature and reinstantiate the database
>> - Any other Pros and Cons for both option as well as any good Link to
>> be checked.
>> TIA
>> Sanjay
> --
> Mladen Gogala
> Oracle DBA

Received on Wed May 06 2015 - 17:23:29 CEST

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