In part 1 of this series, we have discussed why Oracle Data Guard and Active Data Guard make sense for your disaster recovery systems.  It helps you protect your data, while also bringing down the cost of a disaster recovery solution that is turning off a lot of CIO, IT Managers and other decision-makers from implementing a disaster recovery solution for their businesses.

Today, let us compare Active Data Guard and remote storage mirroring.  Who wins?

Active Data Guard vs. Remote Storage Mirroring

Remote mirroring was the most widely used method to give businesses a real time disaster recovery solution for Oracle Database.  It is basically what is called a generic infrastructure solution, which basically copy everything that is written on your primary volume to a remote volume.  As such, it needs to write a ridiculously big amount of data that would include the writes made to undo files, temp files, data files, archive log files, control files, online redo logs files and other files.  Plus, remote mirroring would need to replicate the entire block even when only a small amount of data was added or changed.  That is an additional one to four megabytes to copy every time your data changes, even slightly.

Active Data Guard, on the other hand, isolates the changes in your online redo log files, which is basically a very small portion of your write volume.

So what happens is that you have 7x more network volume, 27x network I/O and no production offload when you use remote mirroring.

This is also a problem when you make a mistake when administering your Oracle Database.  For instance, you accidentally deleted log files in your primary.  That mistake will also be replicated to your remote mirror, but because Active Data Guard allows you to isolate the changes made to the database and validates all changes, this mistake will not be copied to your backups.

At this point, if you insist on using remote mirroring, you will need to make use of a storage snap-shot software to ensure that if you do make mistakes that would render both your primary and remote volumes unusable, you could still do a “point in time recovery”.

In short, Oracle Active Data Guard is better than remote storage mirroring because you get continuous application level validation in real time.  As soon as there are changes in your application, Active Data Guard will be able to capture it.  Anything that is not important will not be copied.  Every time your database goes offline, your disaster recovery system is always ready for failover.

Data Guard also beats remote mirroring in giving you higher availability because it gives you automatic failover to a new primary database if your current database gives out, with no data loss whatsoever, or within the accepted level of data loss.  Even during a planned upgrade of your database, Data Guard gives you maximum availability by letting you upgrade and do maintenance on a standby database.  You can test and implement the standby database and then use this as your primary.  You are offline for a maximum of 60 seconds if you are using a single Oracle Database.

Are you tired of using remote mirroring for your backups?  Call Four Cornerstone today! We can help you use Oracle Data Guard and Active Data Guard.

Photo by Oracle.