I agree – a back out becomes practically very challenging after the second node is upgraded, because the new data is written in the new disk format. To satisfy the “you must have a backout” rules, I just say that after node 1, I could stop that node, wipe the data, downgrade the binaries, and replace that node back to the original version (and yes, there could still be consistency problems with that). There is no going back after node 2. And I have never needed to try and go back, either. Test well in NP, and be ready to tackle any PR problems to keep going forward.
Sean Durity From: Erick Ramirez <erick.rami...@datastax.com> Sent: Tuesday, March 3, 2020 11:35 PM To: user@cassandra.apache.org Subject: Re: [EXTERNAL] Cassandra 3.11.X upgrades Should upgradesstables not be run after every node is upgraded? If we need to rollback then we will not be able to downgrade sstables to older version You can choose to (a) upgrade the SSTables one node at a time as you complete the binary upgrade, or (b) upgrade the binaries on all nodes then perform the SSTables upgrade in one hit. The choice is up to you but beware of the following caveats: - there's a performance hit when C* reads "n - 1" versions of SSTables so the sooner you do it the better - upgrading SSTables one node at a time is preferable due to the considerable performance hit or schedule it during low traffic periods The idea of a rollback isn't what you're accustomed to. There is no concept of "downgrade" in Cassandra. If you decide to rollback or backout of an upgrade implementation, it means that you have to restore your cluster from backups so be aware of that too. This is because once you've performed an upgrade, things like schema and system tables are generally no longer backward-compatible. Also, new incoming mutations are written in the new format which again is not backward-compatible. To cut to the chase -- the decision to upgrade the SSTables has zero bearing on rollback. Cheers! ________________________________ The information in this Internet Email is confidential and may be legally privileged. It is intended solely for the addressee. Access to this Email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. When addressed to our clients any opinions or advice contained in this Email are subject to the terms and conditions expressed in any applicable governing The Home Depot terms of business or client engagement letter. The Home Depot disclaims all responsibility and liability for the accuracy and content of this attachment and for any damages or losses arising from any inaccuracies, errors, viruses, e.g., worms, trojan horses, etc., or other items of a destructive nature, which may be contained in this attachment and shall not be liable for direct, indirect, consequential or special damages in connection with this e-mail message or its attachment.
