Re: [Postgres-xc-general] what is the performance drop because of the synchronous GTM status backup to GTM-standby

[Nikhil S. <ni...@st...>]

Hi Prasad,

1) I am trying to evaluate the High Availability aspects of PGXC; and
> notice that GTM, and GTM-standby are configured to be in continuous
> sync. That means, every status change in GTM is synchronously made at
> GTM-standby.  In such setup, what is the performance drop becoz of
> gtm-standby.
>
> Are there any benchmark tests run with and without GTM-standby?? what
> are the numbers??
>
>
We did not see any significant differences in the with and without
GTM-Standby numbers when we did the runs some while ago. Don't have more
specifics right now though.



> 2) How is GTM failure discovered? Vanilla PGXC, doesn't integrate with
> clusters like Corosync, right??
>
>
You can come up with your resource agents for Corosync/Pacemaker. That's
what we did at StormDB. We have agents for GTM and datanode failover.


> 3) During GTM-failover, I see bunch of manual steps are needed to
> promote the GTM-standby to master; and make the GTM-proxies reconnect
> to the new GTM. What happens to the in-flight and new transactions
> while this GTM-failover happening??
> I guess all active transaction will have to hang during this period,
> isn't??
>
>
Again if you integrate properly with Corosync/Pacemaker or have your own HA
infrastructure in place, then you won't need any manual steps.

Transactions would fail or error out for a brief period when this is
happening. If the application has logic to retry the transactions then it
might help.

Regards,
Nikhils


> thanks,
> -Prasad
>
>
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