Re: [GENERAL] Streaming Replication archive_command is really needed?

2017-07-21 Thread Michael Paquier 
On Fri, Jul 21, 2017 at 8:15 AM, Andreas Kretschmer
 wrote:
> Am 21.07.2017 um 08:01 schrieb Michael Paquier:
>> "No" is not completely exact and lacks in details. There are two cases
>> where having an archive is helpful:
>> 1) The standby has disconnected from its primary for a time long
>> enough that WAL segments have been rotated by two completed
>> checkpoints. If that happens, when the standby reconnects it would
>> fail, and you would need to take a new base backup.
>
> you can prevent that using replication slots, but i'm pretty sure you
> (Michael) knows that ;-)
> http://paquier.xyz/postgresql-2/postgres-9-4-feature-highlight-replication-phydical-slots/

There is a typo on my URL here. Well that's too late to fix it even if
that's bad style.

>> 2) Backup strategies. Keeping a larger history set of WAL segments is
>> helpful for incremental backups, which is partially the point actually
>> raised upthread about PITR.
>
> Ack, that's right. Using both (streaming and wal-shipping/archiving) will
> make it more robust, and you have (with archiving) the posibility for PITR.
> BUT, you can build a streaming replication without archiving, even you can
> build a continuous backup using only streaming (Barman, streaming only
> mode).

Backup solutions developed by experts on the topic are paths to reliability.
-- 
Michael


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Re: [GENERAL] Streaming Replication archive_command is really needed?

2017-07-21 Thread Andreas Kretschmer 



Am 21.07.2017 um 08:01 schrieb Michael Paquier:

On Thu, Jul 20, 2017 at 10:07 PM, Leonardo M. Ramé  wrote:

El 20/07/17 a las 16:57, Andreas Kretschmer escribió:

On 20 July 2017 21:46:09 GMT+02:00, "Leonardo M. Ramé"
 wrote:

Hi, I wonder if archive_mode=on and archive_command parameters in
postgresql.conf are really needed for streaming replication between two

servers (master-slave).

No.

So, can I just comment those commands and remove the main/archive directory?

"No" is not completely exact and lacks in details. There are two cases
where having an archive is helpful:
1) The standby has disconnected from its primary for a time long
enough that WAL segments have been rotated by two completed
checkpoints. If that happens, when the standby reconnects it would
fail, and you would need to take a new base backup.


you can prevent that using replication slots, but i'm pretty sure you 
(Michael) knows that ;-)
( 
http://paquier.xyz/postgresql-2/postgres-9-4-feature-highlight-replication-phydical-slots/ 
)




2) Backup strategies. Keeping a larger history set of WAL segments is
helpful for incremental backups, which is partially the point actually
raised upthread about PITR.


Ack, that's right. Using both (streaming and wal-shipping/archiving) 
will make it more robust, and you have (with archiving) the posibility 
for PITR.
BUT, you can build a streaming replication without archiving, even you 
can build a continuous backup using only streaming (Barman, streaming 
only mode).



Regards, Andreas

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Re: [GENERAL] Streaming Replication archive_command is really needed?

2017-07-21 Thread Michael Paquier 
On Thu, Jul 20, 2017 at 10:07 PM, Leonardo M. Ramé  wrote:
> El 20/07/17 a las 16:57, Andreas Kretschmer escribió:
>> On 20 July 2017 21:46:09 GMT+02:00, "Leonardo M. Ramé"
>>  wrote:
>>>
>>> Hi, I wonder if archive_mode=on and archive_command parameters in
>>> postgresql.conf are really needed for streaming replication between two
>>>
>>> servers (master-slave).
>>
>> No.
>
> So, can I just comment those commands and remove the main/archive directory?

"No" is not completely exact and lacks in details. There are two cases
where having an archive is helpful:
1) The standby has disconnected from its primary for a time long
enough that WAL segments have been rotated by two completed
checkpoints. If that happens, when the standby reconnects it would
fail, and you would need to take a new base backup.
2) Backup strategies. Keeping a larger history set of WAL segments is
helpful for incremental backups, which is partially the point actually
raised upthread about PITR.
-- 
Michael


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Re: [GENERAL] Streaming Replication archive_command is really needed?

2017-07-20 Thread Achilleas Mantzios 

On 20/07/2017 23:07, Leonardo M. Ramé wrote:



El 20/07/17 a las 16:57, Andreas Kretschmer escribió:

On 20 July 2017 21:46:09 GMT+02:00, "Leonardo M. Ramé"  
wrote:

Hi, I wonder if archive_mode=on and archive_command parameters in
postgresql.conf are really needed for streaming replication between two

servers (master-slave).

Regards,


No.

Andreas



So, can I just comment those commands and remove the main/archive directory?

You'll lose the capability of PITR. Also what do you mean main/archive 
directory? I hope you don't mean data/pg_xlog .


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Achilleas Mantzios
IT DEV Lead
IT DEPT
Dynacom Tankers Mgmt



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Re: [GENERAL] Streaming Replication archive_command is really needed?

2017-07-20 Thread Leonardo M . Ramé 



El 20/07/17 a las 16:57, Andreas Kretschmer escribió:

On 20 July 2017 21:46:09 GMT+02:00, "Leonardo M. Ramé"  
wrote:

Hi, I wonder if archive_mode=on and archive_command parameters in
postgresql.conf are really needed for streaming replication between two

servers (master-slave).

Regards,


No.

Andreas



So, can I just comment those commands and remove the main/archive directory?

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Medical IT - Griensu S.A.
Av. Colón 636 - Piso 8 Of. A
X5000EPT -- Córdoba
Tel.: +54(351)4246924 +54(351)4247788 +54(351)4247979 int. 19
Cel.: +54 9 (011) 40871877


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Re: [GENERAL] Streaming Replication archive_command is really needed?

2017-07-20 Thread Andreas Kretschmer 
On 20 July 2017 21:46:09 GMT+02:00, "Leonardo M. Ramé"  
wrote:
>Hi, I wonder if archive_mode=on and archive_command parameters in 
>postgresql.conf are really needed for streaming replication between two
>
>servers (master-slave).
>
>Regards,

No.

Andreas


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[GENERAL] Streaming Replication archive_command is really needed?

2017-07-20 Thread Leonardo M . Ramé 
Hi, I wonder if archive_mode=on and archive_command parameters in 
postgresql.conf are really needed for streaming replication between two 
servers (master-slave).


Regards,
--
Leonardo M. Ramé
Medical IT - Griensu S.A.
Av. Colón 636 - Piso 8 Of. A
X5000EPT -- Córdoba
Tel.: +54(351)4246924 +54(351)4247788 +54(351)4247979 int. 19
Cel.: +54 9 (011) 40871877


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