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From "Durity, Sean R" <SEAN_R_DUR...@homedepot.com>
Subject RE: [EXTERNAL] Re: Rolling back Cassandra upgrades (tarball)
Date Mon, 01 Oct 2018 13:18:29 GMT
Version choices aside, I am an advocate for forward-only (in most cases). Here is my reasoning,
so that you can evaluate for your situation:
- upgrades are done while the application is up and live and writing data (no app downtime)
- the upgrade usually includes a change to the sstable version (which is unreadable in the
older version)
- any data written to upgraded nodes will be written in the new sstable format
+ this includes any compaction that takes place on upgraded nodes, so even an app outage doesn't
protect you
- so, there is no going back, unless you are willing to lose new (or compacted) data written
to any upgraded nodes

As you can tell, if the assumptions don't hold true, a roll back may be possible. For example,
if the sstable version is the same (e.g., for a minor upgrade), then the risk of lost data
is gone. Or, if you are able to stop your application during the upgrade process and stop
compaction. Etc.

You could upgrade a single node to see how it behaves. If there is some problem, you could
wipe out the data, go back to the old version, and bootstrap it again. Once I get to the 2nd
node, though, I am only going forward.

Sean Durity


-----Original Message-----
From: Jeff Jirsa <jjirsa@gmail.com>
Sent: Sunday, September 30, 2018 8:38 PM
To: user@cassandra.apache.org
Subject: [EXTERNAL] Re: Rolling back Cassandra upgrades (tarball)

Definitely don’t go to 3.10, go to 3.11.3 or newest 3.0 instead


--
Jeff Jirsa


On Sep 30, 2018, at 5:29 PM, Nate McCall <zznate.m@gmail.com> wrote:

>> I have a cluster on v3.0.11 I am planning to upgrade this to 3.10.
>> Is rolling back the binaries a viable solution?
>
> What's the goal with moving form 3.0 to 3.x?
>
> Also, our latest release in 3.x is 3.11.3 and has a couple of
> important bug fixes over 3.10 (which is a bit dated at this point).
>
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