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AnshulFarkya-7260 asked ·

Azure SQL Database: Geo - replication - DR node compute

Hello,

For a geo-replication configuration in Azure SQL database, Can we have server less compute for replicated node in other region, while having provisioned compute in primary region?
What could be the challenges we can face for having this configuration in place?

Thanks.
Best Regards,
Anshul

azure-sql-database
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1 Answer

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KalyanChanumolu-MSFT answered ·

@AnshulFarkya-7260 Thank you for reaching out.
You can configure the GeoReplicated secondary as a serverless database. The primary database should be in a vCore pricing model.

Although technically possible, the general recommendation is to have both primary and secondary databases on the same service tier.
If the primary database is experiencing a heavy write workload, a secondary with lower compute size may not be able to keep up with it.
That will cause redo lag on the secondary, and potential unavailability of the secondary. To mitigate these risks, active geo-replication will throttle the primary's transaction log rate if necessary, to allow its secondaries to catch up.

More on this topic is here

Please let us know if you have any further questions.


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Thanks Kalyan for answering it.

Is it a good practice to use secondary server less database with minimum and maximum (same as primary database) CPU values defined? In that way it can scale up resources when needed to catch up with primary database? This way we can save some cost when system is not loaded. Thoughts?


Best Regards,
Anshul

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KalyanChanumolu-MSFT avatar image KalyanChanumolu-MSFT AnshulFarkya-7260 ·

@AnshulFarkya-7260 It depends on how you want to use the secondary, are there applications that read from the secondary occasionally? Are there continuous writes on the primary database?

If you have off-peak hours for your application where the primary doesn't receive many writes during for an extended period, then a serverless secondary makes sense.

When cost is the major concern, I have seen some customers create the secondary database in an elastic pool shared with other databases in their enterprise. You will need to test and evaluate what suits your requirement best.

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