Re: PostgreSQL File System Based Backup Restartability

girish R G peetle <giri(dot)anamika0(at)gmail(dot)com> writes:

> Thanks Kevin.
>
> "Be careful that when you resume after such an interruption you do
> not skip any files and that you complete or re-copy any files that
> were partially copied before the problems."
>
> Here you mean, we should not skip any files that was already backed up before interruption ?
>  I will have to backup entire content under DATA directory again ?

False.

Any file already copied and known copied thoroughly should not require
copying again.

The file under copy when the network drop occurred needs copying again
and/or syncing if your copy program knows how to do that without moving
all bits... and of course all missing files need copying also.

HTH

> Thanks
> Girish
>
> On Tue, Feb 17, 2015 at 10:04 PM, Kevin Grittner <kgrittn(at)ymail(dot)com> wrote:
>
> girish R G peetle <giri(dot)anamika0(at)gmail(dot)com> wrote:
>
> > Steps
> > - Database size is 1 TB
> > - I'll execute pg_start_backup('label');
> > - I will traverse through the DATA directory to get the list of
> >   directories and files.
> > - I will start moving the files to backup media. ( over network )
> > - When I'm half way (500GB done), network error happens. So
> >   movement of files is halted.
> > - Network issue is resolve after 30 minutes (In this time files
> >   might have got deleted or added with creation/deletion of
> >   database/tables )
> > - I'll resume moving the files to backup media from where it had
> >   halted.
> > - When movement of files is done, I'll execute pg_stop_backup()
> > - I'll move all the transaction logs that got archived to backup
> >   media.
> >
> > Is PostgreSQL server recovery to a consistent state possible with
> > backup content obtained from above steps ?
>
> As long as you follow all the rules for what files to copy (and not
> copy), you should have a good backup.  Some things to be careful
> about that I've seen people get wrong with some frequency:
>
> - Be sure to exclude all files in and under the pg_xlog directory.
>   The backup should contain the directory itself, and it is best to
>   include its subdirectory, but copying the files can cause
>   corruption.
> - Exclude the postmaster.pid file.
> - Be sure *not* to exclude the backup_label file.  Without this
>   file, restoring from the backup may or may not have corruption,
>   which may or may not be initially apparent.
>
> Be careful that when you resume after such an interruption you do
> not skip any files and that you complete or re-copy any files that
> were partially copied before the problems.
>
> --
> Kevin Grittner
> EDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>

--
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres(dot)consulting(at)comcast(dot)net
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