I am testing the upgrade of a Cassandra cluster from version 3.11.4 to 4.0.1 and, viceversa, the subsequent downgrade from 4.0.1 to 3.11.4, to better understand all the steps and possible rollback. While the upgrade step is smooth and easy to perform, the downgrade presents a big problem: the new SStables are incompatible with the older version, and the tool sstableupgrade does not seem to work. Is there a way to rollback an upgrade procedure or is it totally not possible?
Thank you in advance.
I agree with @smadhavan with an addition in that if you don't have multiple DC's, you could do a backup before the upgrade. Then if you want to roll back, you would restore back those sstables from the 3.11.x version.
With the above said, if you have multiple DC's that's a much easier option.
Thank you all for your replies: so, no way for now, to downgrade the upgraded SSTables, better to take a snapshot before upgrade or to use a second datacenter for data recovery, if possible.
Clear, I will test both solutions, thank you again.
@a.porfirio_45462, if you've replication happening to more than 1 datacenter (DC), you could start the upgrade from 3.11.x to 4.0.x and complete it just on the 1st DC and then for rollback install the old version to replicate from the other DC. I am not sure if there is a direct downgrade option available in this route. Other resources to explore are below,
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