CosmosDB Mongo vCore: cannot scale the cluster down to the M25 tier

Question

Hi all,

I'm trying to scale down a CosmosDB Mongo vCore cluster currently in the M30 tier, to the M25 (burstable) tier. The operation quickly flashes the screen without any message or warning.

Checking the activity logs I can see that the operation fails with the following message:

Down scaling from 'M30' cluster tier to 'M25' cluster tier is not available.

I tried performing first a scale-up to the M40 tier, then to the M25 tier, without success, as it failed the same way:

Down scaling from 'M40' cluster tier to 'M25' cluster tier is not available.

From the M40 to the M30 the operation completed successfully.

When selecting the M25 tier in the Azure Portal I see this message:

Upgrades involving Free or Burstable cluster tier require first upgrading the cluster tier, after which other configurations can be updated.

I could not understand what the message means, and the product documentation is not clear about it as well.

The AI assistant suggested to perform the upgrade sequence M30 to M40, then to M25, but it didn't work as I explained above.

Any help will be much appreciated.

Answer 1

Hi, @Alexandre Silva Thanks for posting your question in the Microsoft Q&A forum.

Thanks for bringing this up, I agree that the message is confusing, and we'll make sure to address it with the team. We'll update the documentation and rectify the messaging accordingly.,

To answer your question scaling down to an M25 isn't supported in Azure Cosmos DB for Mongo Vcore.

Regards

Geetha

Answer 2

The message "Down scaling from 'M30' cluster tier to 'M25' cluster tier is not available" indicates that it is not possible to scale down from M30 to M25 directly. According to the documentation, when upgrading to a Free or Burstable cluster tier, it is necessary to first upgrade to a regular tier and then downgrade to the desired Free or Burstable tier. Therefore, to scale down to M25, you need to first upgrade to a higher tier, such as M40, and then downgrade to M25. This should allow you to scale down to the Burstable M25 tier.

Here are the steps to follow to scale down to M25:

1. Upgrade your cluster to a higher tier, such as M40, using the Azure portal.
2. Wait for the upgrade to complete successfully.
3. Downgrade your cluster to the Burstable M25 tier.

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References:

• Burstable Tier (M25) on Azure Cosmos DB for MongoDB vCore
• Scaling and configuring Your Azure Cosmos DB for MongoDB vCore cluster