MongoDB - wrong version - upgrade to 11.36.68

Question

Hi, We’ve upgrade from v 11.36.49 to 11.36.68.

The upgrade appeared to complete successfully on the Commserve, however I noticed the MongoDB service was failing to start and kept retrying.
From the logs I can see the error “featurecompatibilityversion 4.2 expected 6.0 or 6.3 or 7.0”.

On further investigation I can see the mongod.exe has been upgraded to v7 however the featurecompatibility has been left as 4.2. Replacing the .exe with a version 4.2 has resolved the issue, services start and all ok.

My questions are, I’ve seen the kb about manually upgrading minor versions, but how is it possible to upgrade to v7? CV doesn’t support manually upgrading major version.
Will running v4.2 cause any problems, it appears to have been fine for the last few days since I’ve done this.
Will this resolve in the next upgrade? Is this a known issue for 11.36.68?

Dheeraj Shetty · Accepted Answer

Hi ​@Rafter,I understand, following the upgrade from Commvault 11.36.49 to 11.36.68, the MongoDB service failed to start due to a version mismatch. While the mongod.exe binary was upgraded to v7.0, the featureCompatibilityVersion (FCV) remained at 4.2, causing the service to crash with an error indicating an unsupported FCV.Temporarily reverting to the 4.2 binary resolved the issue, but this configuration is unsupported and may lead to service instability or data issues.Major MongoDB version upgrades (e.g., 4.2 → 7.0) are performed automatically during Commvault platform upgrades if the environment supports it.Manually downgrading binaries is not recommended and may cause data corruption.This mismatch suggests the MongoDB upgrade or FCV update was incomplete or failed during the process. This is not listed as a known issue in 11.36.68, but can be due to upgrade inconsistencies.Would request to revert to the expected MongoDB v7.0.15 binary and update the featureCompatibilityVersion to 7.0.Kindly refer the following KB Article :https://kb.commvault.com/article/54270. And verify what version of OS is installed on the CommServ??MongoDB 7.0 -> Platform Release 2023E (11.36) -> MongoDB 7.0 is not supported for Windows 2016. In this case, MongoDB 6.0 is installed.Regards,Dheeraj

Rafter · Answer

Thanks for the KB, I’d not seen that one.We’ve run a repair from the installer, this has completed the upgrade successfully and has resolved the issue.

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