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* Synchronous replication question
@ 2015-07-07 17:45 CS DBA <cs_dba@consistentstate.com>
0 siblings, 2 replies; 3+ messages in thread
From: CS DBA @ 2015-07-07 17:45 UTC (permalink / raw)
To: pgsql-admin
All;
The docs specify this (9.4 docs):
Synchronous replication offers the ability to confirm that all changes
made by a transaction have been transferred to /*one*/ synchronous
standby server. This extends the standard level of durability offered by
a transaction commit. This level of protection is referred to as 2-safe
replication in computer science theory.
Does this mean that Synchronous replication only works with one standby?
Thanks in advance
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Synchronous replication question
@ 2015-07-07 18:01 Keith <keith@keithf4.com>
parent: CS DBA <cs_dba@consistentstate.com>
1 sibling, 0 replies; 3+ messages in thread
From: Keith @ 2015-07-07 18:01 UTC (permalink / raw)
To: CS DBA <cs_dba@consistentstate.com>; +Cc: pgsql-admin
On Tue, Jul 7, 2015 at 1:45 PM, CS DBA <cs_dba@consistentstate.com> wrote:
> All;
>
> The docs specify this (9.4 docs):
>
> Synchronous replication offers the ability to confirm that all changes
> made by a transaction have been transferred to *one* synchronous standby
> server. This extends the standard level of durability offered by a
> transaction commit. This level of protection is referred to as 2-safe
> replication in computer science theory.
>
> Does this mean that Synchronous replication only works with one standby?
>
> Thanks in advance
>
No, it means that it requires, at minimum, one standby to confirm that the
transaction has been committed there before the master confirms it back to
the client. Look at this section of the docs
http://www.postgresql.org/docs/9.4/static/warm-standby.html#SYNCHRONOUS-REPLICATION
http://www.postgresql.org/docs/9.4/static/runtime-config-replication.html#GUC-SYNCHRONOUS-STANDBY-NA...
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Synchronous replication question
@ 2015-07-07 18:03 Payal Singh <payal@omniti.com>
parent: CS DBA <cs_dba@consistentstate.com>
1 sibling, 0 replies; 3+ messages in thread
From: Payal Singh @ 2015-07-07 18:03 UTC (permalink / raw)
To: CS DBA <cs_dba@consistentstate.com>; +Cc: pgsql-admin
As per
http://www.postgresql.org/docs/9.4/static/runtime-config-replication.html#GUC-SYNCHRONOUS-STANDBY-NA...
at any time the primary waits for ACK from just one standby server in the
list. (The first one, and if its not available, the second one and so on).
So even if something goes amiss with the synchronous slave, the secondary
slave will become synchronous provided its listed in
synchronous_standby_names.
Payal Singh,
Database Administrator,
OmniTI Computer Consulting Inc.
Phone: 240.646.0770 x 253
On Tue, Jul 7, 2015 at 1:45 PM, CS DBA <cs_dba@consistentstate.com> wrote:
> All;
>
> The docs specify this (9.4 docs):
>
> Synchronous replication offers the ability to confirm that all changes
> made by a transaction have been transferred to *one* synchronous standby
> server. This extends the standard level of durability offered by a
> transaction commit. This level of protection is referred to as 2-safe
> replication in computer science theory.
>
> Does this mean that Synchronous replication only works with one standby?
>
> Thanks in advance
>
^ permalink raw reply [nested|flat] 3+ messages in thread
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2015-07-07 18:03 ` Payal Singh <payal@omniti.com>
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