Re: pg_basebackup && long time storage of wal_archive/ content

On 4/14/20 11:16 PM, Matthias Apitz wrote:
> El día Dienstag, April 14, 2020 a las 08:28:35 -0700, Adrian Klaver escribió:
> 
>> On 4/14/20 8:00 AM, Matthias Apitz wrote:
>>>
>>> Hello,
>>>
>>> The run (as user 'postgres') on the server of the cmd:
>>>
>>> pg_basebackup -U ${DBSUSER} -Ft -z -D /data/postgresql11/backup-wal_archive-20200414-1/
>>>
>>> produces correctly the following situtation on the server:
>>>
>>> srap32dxr1:/data/postgresql11 # ls -ltrh backup-20200414-1
>>> total 1.7G
>>> -rw------- 1 postgres postgres 1.7G Apr 14 16:20 base.tar.gz
>>> -rw------- 1 postgres postgres  17K Apr 14 16:20 pg_wal.tar.gz
>>> srap32dxr1:/data/postgresql11 # ls -ltrh data/pg_wal
>>> total 81M
>>> -rw------- 1 postgres postgres 16M Apr 14 15:11 000000010000000C0000009F
>>> -rw------- 1 postgres postgres 16M Apr 14 15:20 000000010000000C000000A0
>>> -rw------- 1 postgres postgres 16M Apr 14 16:10 000000010000000C000000A1
>>> -rw------- 1 postgres postgres 16M Apr 14 16:20 000000010000000C000000A2
>>> -rw------- 1 postgres postgres 342 Apr 14 16:20 000000010000000C0000009D.00000028.backup
>>> drwx------ 2 postgres postgres 36K Apr 14 16:25 archive_status
>>> -rw------- 1 postgres postgres 16M Apr 14 16:50 000000010000000C0000009E
>>> srap32dxr1:/data/postgresql11 # ls -ltrh wal_archive/
>>> total 49M
>>> -rw------- 1 postgres postgres 16M Apr 14 15:20 000000010000000C0000009B
>>> -rw------- 1 postgres postgres 16M Apr 14 16:10 000000010000000C0000009C
>>> -rw------- 1 postgres postgres 16M Apr 14 16:20 000000010000000C0000009D
>>> -rw------- 1 postgres postgres 342 Apr 14 16:20 000000010000000C0000009D.00000028.backup
>>>
>>> The content of the dir wal_archive/ is growing and growing over the
>>> time.
>>>
>>> The pg_wal.tar.gz contains:
>>>
>>> srap32dxr1:/data/postgresql11 # tar tzf backup-20200414-1/pg_wal.tar.gz
>>> 000000010000000C0000009D
>>>
>>> i..e. the files 000000010000000C0000009B ... 000000010000000C0000009D
>>> could be removed in wal_archive/
>>>
>>> Correct? Or how is the long time storage of this dir?
>>
>> pg_basebackup is a point in time backup tool.
> 
> Adrian,
> 
> Thanks for the answer. What do you mean by 'point in time backup tool'?

That pg_basebackup captures the state of the cluster at some point in 
time. As you have found out keeping up with the current state of the 
cluster requires further work. Laurenz provided one built in tool for 
doing that. The other tools I posted earlier also provide means of 
keeping backups consistent.

> And, coming back to my question, can older WAL in wal_archive/ be
> removed without any risks if the daily
> 
> pg_wal.tar.gz
> base.tar.gz
> 
> are moved to a safe place?
> 
>> If you want something that
>> continuously archives and prunes as it goes then you probably want to look
>> at the tools below:
>>
>> https://pgbackrest.org/
>>
>> https://www.pgbarman.org/
>>
>> https://postgrespro.github.io/pg_probackup/
> 
> 
> Thanks, I will have a look into the tools.
> 
>     matthias
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com