Обсуждение: backups and WAL

Hi, first of all thanks for postgresql, it has never given a problem
and is performing great.

Now my question: my employer wants to do backups every 12 hours, and
save the logs evry 2 hours to... Can I simply save the logs
(cp pg_xlog/* ...) or do I need something more elaborate?

Now in a restore situation ... I restore the database, and then what?
put the saved files back in the pg_xlog/ dir, then start postmaster
and magically all starts working? Am I correct or completely insane?
The documentation is not clear in that aspect...

Thanks in advance,
Pablo.

pablobarbachano@yahoo.es wrote:

> Hi, first of all thanks for postgresql, it has never given a problem
> and is performing great.
>
> Now my question: my employer wants to do backups every 12 hours, and
> save the logs evry 2 hours to... Can I simply save the logs
> (cp pg_xlog/* ...) or do I need something more elaborate?
>
> Now in a restore situation ... I restore the database, and then what?
> put the saved files back in the pg_xlog/ dir, then start postmaster
> and magically all starts working? Am I correct or completely insane?
> The documentation is not clear in that aspect...

I suppose that you use a pre 8.0 version, if yes take a look at:

http://www.postgresql.org/docs/7.4/interactive/backup.html


take also a look at PITR available in the future ( near I hope :-) )
8.0:

http://developer.postgresql.org/docs/postgres/backup-online.html



Regards
Gaetano Mendola

On this issue,

   Is a good idea to ln -s the pg_xlog directory onto another place, while the postmaster is running?

    I agree with pablo, documentation at this point is not easy to found.

Regards,

> pablobarbachano@yahoo.es wrote:
>
> > Hi, first of all thanks for postgresql, it has never given a problem
> > and is performing great.
> >
> > Now my question: my employer wants to do backups every 12 hours, and
> > save the logs evry 2 hours to... Can I simply save the logs
> > (cp pg_xlog/* ...) or do I need something more elaborate?
> >
> > Now in a restore situation ... I restore the database, and then what?
> > put the saved files back in the pg_xlog/ dir, then start postmaster
> > and magically all starts working? Am I correct or completely insane?
> > The documentation is not clear in that aspect...
>
> I suppose that you use a pre 8.0 version, if yes take a look at:
>
> http://www.postgresql.org/docs/7.4/interactive/backup.html
>
>
> take also a look at PITR available in the future ( near I hope :-) )
> 8.0:
>
> http://developer.postgresql.org/docs/postgres/backup-online.html
>
>
>
> Regards
> Gaetano Mendola
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 3: if posting/reading through Usenet, please send an appropriate
>       subscribe-nomail command to majordomo@postgresql.org so that your
>       message can get through to the mailing list cleanly

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

G u i d o B a r o s i o wrote:

| On this issue,
|
|
|
|    Is a good idea to ln -s the pg_xlog directory onto another place, while the postmaster is running?

I don't think so



|     I agree with pablo, documentation at this point is not easy to found.

I disagree instead:

1) Go on the first doc page:  http://www.postgresql.org/docs/7.4/interactive/index.html
2) Search for backups
3) The first 4 entries are what you have to know

Please do not take this as RTFM




Regards
Gaetano Mendola



-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (MingW32)
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

iD8DBQFBLwQR7UpzwH2SGd4RAltoAKCMvcXuH4zbwleLDJaXXZ+tu6Q+/ACg5jB1
KvTAP2TiX5ZWFXiKvSTRIW0=
=GS6b
-----END PGP SIGNATURE-----

What I meant(And I guess that Pablo asked for this also), was that is not easy to found information or howto work on
thepg_xlog directory.  

I didn't take it as "read the FINE manual" anyway ;)

Regards,
Guido

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> G u i d o B a r o s i o wrote:
>
> | On this issue,
> |
> |
> |
> |    Is a good idea to ln -s the pg_xlog directory onto another place, while the postmaster is running?
>
> I don't think so
>
>
>
> |     I agree with pablo, documentation at this point is not easy to found.
>
> I disagree instead:
>
> 1) Go on the first doc page:  http://www.postgresql.org/docs/7.4/interactive/index.html
> 2) Search for backups
> 3) The first 4 entries are what you have to know
>
> Please do not take this as RTFM
>
>
>
>
> Regards
> Gaetano Mendola
>
>
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.2.4 (MingW32)
> Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org
>
> iD8DBQFBLwQR7UpzwH2SGd4RAltoAKCMvcXuH4zbwleLDJaXXZ+tu6Q+/ACg5jB1
> KvTAP2TiX5ZWFXiKvSTRIW0=
> =GS6b
> -----END PGP SIGNATURE-----
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: you can get off all lists at once with the unregister command
>     (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)

pablobarbachano@yahoo.es writes:
> Now my question: my employer wants to do backups every 12 hours, and
> save the logs evry 2 hours to... Can I simply save the logs
> (cp pg_xlog/* ...) or do I need something more elaborate?

You can't realistically do this in any pre-8.0 release; it's perhaps
doable in theory but there are too many gotchas to consider it a
trustworthy backup technique.

8.0 will have real support for log-based backup.  Feel free to try out a
beta --- we could use more people testing this feature.

            regards, tom lane