Downgrading from 3.11.5 to 3.11.0

[Surbhi Gupta <su...@gmail.com>]

Hi,

As the SSTable file formats have changed from 3.11.4 to "md "
https://docs.datastax.com/en/landing_page/doc/landing_page/compatibility.html

We are going to take snapshots but still wanted to understand .
After we do upgrades stable when we upgrade from 3.11.0 to 3.11.5 , and
later in future if we found any issue , then can we downgrade to 3.11.0
with SSTable format "md" (we may not be able to restore from the snapshot
if time lapse is between upgrades is more) .

Any thoughts?

Thanks
Surbhi

Re: Downgrading from 3.11.5 to 3.11.0

[Jürgen Albersdorfer <ja...@gmail.com>]

Wow, didn't recognize/expect such fundamental Change in a minor Version. -
But then I can at least say that I have a 21 Node production Cluster
running with all different Versions from 3.11.0 to 3.11.4.

Am Do., 5. März 2020 um 08:09 Uhr schrieb Erick Ramirez <
erick.ramirez@datastax.com>:

> Are you telling me that cassandra changes sstanle file format when
>> updating from 3.11.4 to 3.11.5?
>>
>
> It was introduced in C* 3.0.18 and 3.11.4. The format changed from -mc-
> to -md- because of a bug with min/max clustering values. It had the
> potential to result in data loss so there was no choice but to change the
> format in a minor version (CASSANDRA-14861
> <https://issues.apache.org/jira/browse/CASSANDRA-14861>). Cheers!
>

Re: Downgrading from 3.11.5 to 3.11.0

[Erick Ramirez <er...@datastax.com>]

>
> Are you telling me that cassandra changes sstanle file format when
> updating from 3.11.4 to 3.11.5?
>

It was introduced in C* 3.0.18 and 3.11.4. The format changed from -mc- to
-md- because of a bug with min/max clustering values. It had the potential
to result in data loss so there was no choice but to change the format in a
minor version (CASSANDRA-14861
<https://issues.apache.org/jira/browse/CASSANDRA-14861>). Cheers!

Re: Downgrading from 3.11.5 to 3.11.0

[Jürgen Albersdorfer <ja...@gmail.com>]

Are you telling me that cassandra changes sstanle file format when updating from 3.11.4 to 3.11.5?

Von meinem iPhone gesendet

> Am 05.03.2020 um 02:05 schrieb Sandeep Nethi <ne...@gmail.com>:
> 
> 
> Hi,
> 
> I think there is no way to revert sstables to previous version once they are upgraded and having new transactions on upgraded version.
> 
> But you can try some workarounds by creating a secondary datacenter with 3.11.0 and having the primary datacenter upgraded to 3.11.5. This way if you come across any issues with upgraded datacenter, you can switch your traffic to another datacenter which is on older version (later on you can decommission dc with 3.11.5) but this approach needs to be tested.
> 
> But having two versions in same cluster might have performance impact. 
> 
> Thanks,
> Sandeep
> 
> On Thu, 5 Mar 2020 at 1:51 PM, Erick Ramirez <er...@datastax.com> wrote:
>>> ... the older version of C* will not be able to read the SSTables using the old format.
>> 
>> Sorry, I meant to say "... using the NEW format". Cheers!

Re: Downgrading from 3.11.5 to 3.11.0

[Sandeep Nethi <ne...@gmail.com>]

Hi,

I think there is no way to revert sstables to previous version once they
are upgraded and having new transactions on upgraded version.

But you can try some workarounds by creating a secondary datacenter with
3.11.0 and having the primary datacenter upgraded to 3.11.5. This way if
you come across any issues with upgraded datacenter, you can switch your
traffic to another datacenter which is on older version (later on you can
decommission dc with 3.11.5) but this approach needs to be tested.

But having two versions in same cluster might have performance impact.

Thanks,
Sandeep

On Thu, 5 Mar 2020 at 1:51 PM, Erick Ramirez <er...@datastax.com>
wrote:

> ... the older version of C* will not be able to read the SSTables using
>> the old format.
>>
>
> Sorry, I meant to say *"... using the NEW format"*. Cheers!
>

Re: Downgrading from 3.11.5 to 3.11.0

[Erick Ramirez <er...@datastax.com>]

>
> ... the older version of C* will not be able to read the SSTables using
> the old format.
>

Sorry, I meant to say *"... using the NEW format"*. Cheers!

Re: Downgrading from 3.11.5 to 3.11.0

[Erick Ramirez <er...@datastax.com>]

Once you've upgraded to a version of Cassandra that uses a new SSTable
format, you cannot downgrade the binaries -- for whatever reason -- because
the older version of C* will not be able to read the SSTables using the old
format.

I'm more concerned that you think reverting to a .0 release is a better
option than addressing the issue in the newer version. ;) Cheers!

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