san replication or log shipping

Hi there,

I wanted to get some views on the merits of log shipping v SAN to SAN replication for a large Oracle database. (DR scenario)

The comparison should be made on the fact that we already have SANs in place at both locations and adequate bandwidth to cope.

What are the technical merits of one over the other? Which would you chose?

Thanks
58872Asked:
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AkenathonCommented:
"log shipping" sounds like SQLServer terminlology, in Oracle you're talking about data guard. Anyway, you are getting very different things... I won't be describing SAN replication because it's no mystery, but some differences with data guard include:

- Data guard needs an active instance to apply the logs to the standby database, so you'll be using up some CPU and RAM
- In the event of a disaster on the primary site, you will have another DBMS ready to take over in seconds
- You can set it up so that it applies the logs after some delay, so that if say a table is accidentally dropped at the primary site, you stop applying logs to save your data
- If you set it up correctly, Oracle includes commands to switchover to the standby DB without having to change any configuration in your connecting clients
- It's easier to audit and report what's going on with the redo applying process
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madunix (Fadi SODAH)Chief Information Security Officer Commented:
check out google.com  (San+replication+vs+DataGuard)
http://www.itsarva.com/ittopicsblog/?p=272
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madunix (Fadi SODAH)Chief Information Security Officer Commented:
As said above some applications have their own D/R solutions such as Oracle Data Guard that consume less valuable bandwidth than SAN replication. For example, if you use Oracle DataGaurd instead of remote-copying all Oracle LUN's (data, log,temp, ...), you will save bandwidth, so make sure that the company is ready to pay for higher bandwidth between sites (Production and Resumption Site).

Before discussing bandwidth requirement, it became necessary to really understand the expectations of Resumption site role. Naturally, it would be ideal to have Resumption Site to function as a full
business continuity site. Practically, and largely limited by the communication channel infrastructure that is currently offered by the Communication Providers ISP/Telco, it is not an achievable solution in some cases. Additionally cost/benefit analysis study can shed more light on the feasibility of upgrading to higher bandwidth and finally, the time delay between both locations need to be studied which of course linearly affects data loss during major disaster

You could configure Resumption site as an Oracle Data Guard scenario for the following reasons:
-Offers Backup for database
-Lower Bandwidth requirements
-Simpler in concept
-Much Quicker first copy builds
-Errors in primary sites are not propagated immediately and can be recovered by standard procedures.

Note: data loss due to delays might occur; size of loss can be predicted

In fact, you can open the database in read only mode any time, and in case of disaster, you can switch the database to READ/Write mode. Therefore, it preserves the entire database, but does
not preserve any operating system or networking configuration. With proper manual intervention, you can also configure the network, so that you can access the database through network

Note: Data Guard does not really require SAN/SAN DR to function. It can function as long as
there is oracle installation on both sites with a communication channel in place.

The main challenge in SAN-SAN replication is to have enough bandwidth (media link) for replication... my recommendation fiber media would be the best for SAN replication but it's costly.


http://www.redbooks.ibm.com/abstracts/tips0340.html
http://www-03.ibm.com/systems/business_resiliency/
http://www.ibm.com/itsolutions/disaster-recovery/
http://www-01.ibm.com/software/success/cssdb.nsf/hardwareL2VW?OpenView&Count=30&RestrictToCategory=corp_StorageDS8100&cty=en_us
http://www-01.ibm.com/software/tivoli/products/storage-mgr/
http://www.drj.com/
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58872Author Commented:
Many thanks for the comments. Sorry for delay.
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