Re: base backup from the standby without pg_basebackup

Alexey,

Instead of managing it manually, you should be able to take backup from
slave using OmniPITR <https://github.com/omniti-labs/omnipitr>:
https://github.com/omniti-labs/omnipitr/blob/master/doc/omnipitr-backup-slave.pod

On Thu, Apr 2, 2015 at 6:13 AM, Alexey Klyukin <alexk(at)hintbits(dot)com> wrote:

> Hello,
>
> We had an issue with backing up one of our master servers, since a
> base backup increased the load on the master, resulting in slowdowns
> in the application working with that database. While there are ways to
> overcome this problem by using nice on the backend process doing the
> backup or throttling the network connection, we've decided to use a
> less complicated route of producing a base backup from an almost idle
> standby server.
>
> We don't use pg_basebackup, but our own tool, which does the rsync +
> compression and also symlinks some directories from pg_data (such as
> pg_log or pg_xlog) to the locations on different partitions. So, the
> question is, how would one make a base backup from the [async] standby
> without using pg_basebackup. Our steps were the following:
>
> - make sure WAL files from the master are archived and reachable on
> the new replica host (via NFS).
> - run pg_start_backup('label') on the master
> - initialise a new cluster, rsync files from the replica, create a
> recovery.conf and so on (made by our tool)
> - run pg_stop_backup() on the master.
>
> The new replica did start and were restoring WAL files for a while,
> but eventually we came across the PANIC message:
>
> 2015-03-18 19:10:52.943 CET,,,17293,,55083494.438d,922,,2015-03-17
> 15:05:08 CET,1/0,0,PANIC,XX000,"WAL contains references to invalid
> pages",,,,,"xlog redo visible: rel 1663/16414/24453; blk 26569",,,,""
>
> We did check the disk on that system (and now rechecking the memory),
> but so far the hardware itself looks ok, which makes me wonder if the
> procedure above is flawed? What would be the proper way to produce a
> base backup from the standby without using pg_basebackup?
>
> Both master and replicas are running PostgreSQL 9.3.5.
>
> Kind regards,
> --
> Alexey Klyukin
>
>
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--
Denish Patel,
OmniTI Computer Consulting Inc.
Database Architect,
http://omniti.com/does/data-management
http://www.pateldenish.com