I was recently asked to provide a description of the various modes of operation possible with a standby configuration. This was needed to explain the setup to a group of non-technical managers.
The original setup of this companies dataguard configuration was Maximum Performance but the company was concerned about the potential data loss associated with running in an asynchronous mode.
Below is what I produced for them, nothing particularly revelatory here, but perhaps it might be useful for you if you are having this debate with your management team.
Introduction
When using an Oracle standby database for Business Continuity purposes there are 3 possible modes of operation for determining how the data is sent from the primary (the database currently being used to support the business queries) database to the standby (failover database to be used upon invocation of business continuity) database.
There are 2 synchronous modes and 1 asynchronous mode.
The various modes of operation of a standby are a real trade-off between data protection and impact on the primary systems.
Modes of Operation
The following table shows the options giving the benefits and drawbacks.
|
Mode of Operation |
SYNC/ ASYNC |
Benefits |
Drawbacks |
|
Maximum Protection |
SYNC |
Never any data loss, no data ever accepted on primary |
Slower response times on primary. Network disruption |
|
Maximum Availability |
SYNC |
Updates must be on standby before accepted on primary, |
Slower response times on primary. Data loss possible if |
|
Maximum Performance
|
ASYNC
|
No performance slowdown for applications on primary. |
Data loss will happen |
This customer is currently running in Maximum Performance mode, and thus the standby solution has minimal impact on the response times of the various applications.
There are 2 factors that would impact the application response if they moved to a higher level of data protection, the network latency and the network bandwidth. During normal operation, the response time of applications that make data changes would be impacted by the round trip time (rtt) to their standby
During periods of high volume activity, the bandwidth can become congested and this could lead to significant delay in response time.
Conclusion
If a higher level of data protection was deemed a business requirement I would advise a significantly larger network bandwidth to the Business Continuity site.
During normal running we typically see a transport lag (of data between the sites) of around 10 seconds and this would be the typical amount of data we would lose in a disaster situation. During high peaks of activity this can increase.
In determining to increase the protection mode of the configuration there is a real trade off between how much you value your data (for this customer it is a reputational issue as much as a financial consideration) and the impact on your normal day-to-day performance.
Data Backup
/ January 16, 2009I think that decreasing the number of users per router and installing more of them to increase overall bandwidth of a company is the way to go in order to achieve a higher level of protection. If a network’s running ASYNC on their server, it’s literally as if there is no backup protection. What’s the use? I think it’s essential in this day and age to make sure there’s a backup on site and a cold backup off site in the event of some digital catastrophic system failure or what not. True, the chances of this happening with IT personnel on site 24/7 isn’t as high, but it still exists. Better safe than sorry: SYNC with maximum protection…
vijay
/ April 10, 2012Nice explanation