Re: DataGuard vs Hardware mirroring for DR
Date: Thu, 19 Feb 2009 17:41:11 -0800 (PST)
Message-ID: <b686ef62-f86c-4ba6-a64c-351aeda20ee9_at_k36g2000pri.googlegroups.com>
On Feb 19, 8:44 am, emdproduct..._at_hotmail.com wrote:
> Dear Group,
>
> We are planning for DR site. We have two options, one is DataGuard,
> another is using Hardware SAN mirroring.
>
> Is there any pros and cons in terms of this two methods?
>
> Your help is highly appreciated.
We currently use Data Guard for our DR site using 9.2.0.8. To use it in maximum protection mode you need very high bandwidth, otherwise the primary database will hang while waiting for the standby to write the transactions. If you don't have enough bandwidth (you need to be able to write to both sites at the same speed) then you would need to run in maximum performance which means you can lose data. You can check how much bandwidth you need by running statspack over a very small window in which the database is writing redo at its fastest rate. Also, you can run a ssh pipe over the Data Guard link to push four times more data over it, however, this comes at a cost and is probably only recommended if you are running in MAXIMUM PERFORMANCE mode and even then Oracle don't recommend it (from memory).
I do nearly all of my full and incremental backups on the standby site which takes the load off production as our database is nearly 1TB. I regularly duplicate the full production database on our standby which guarantees that my backups are working correctly. It also allows me to check that the tape silo is working correctly as well. I also do PITR to test that all of the archive logs are being backed up as expected.
I find that Data Guard is extremely reliable, robust and gives me the flexibility to make full production copies without causing a load on the primary. I can then also do full exports of the duplicated database for various reasons.
Also, the switch over from primary to standby works very well with only a few simple commands and minimum downtime.
There are a few problems with controlfile size with Data Guard however. Make sure you do regular maintenance to prevent the controlfiles from growing to large, ie, correct startup parameters and RMAN maintenance. Received on Thu Feb 19 2009 - 19:41:11 CST