Sorry for my sharp reply! It looks like we are after the same thing
so that does help a little although it doesn't really answer my
question. I set up my backups system using pg_dump back in 7.3
because that's all there was. I am finally moving to 8.1 and want to
switch to doing incrementals because the dumps are just getting too
big. If you didn't mind showing me your scripts it would probably be
a good staring point for me.
Thanks,
Rick
On Jan 27, 2006, at 3:32 AM, Csaba Nagy wrote:
OK, that was before going home from work, so it could be excusable :-D
I read your mail now in more detail, and I can't answer it other than
that we use here a standby data base based on WAL log shipping, and
the
procedure of building the standby finishes with a script
inserting/deleting a few 1000s of lines in a bogus table so there
is for
sure a WAL file archived. That might fit your needs or might not...
Cheers,
Csaba.
On Thu, 2006-01-26 at 18:48, Rick Gigger wrote:
Um, no you didn't read my email at all. I am aware of all of that
and it is clearly outlined in the docs. My email was about a
specific detail in the process. Please read it if you want to know
what my actual question was.
Thanks,
Rick
On Jan 26, 2006, at 10:41 AM, Csaba Nagy wrote:
I didn't read your mail very carefully, but I guess you want:
- turn on WAL archiving, and archive all WAL logs;
- take the file system backup at regular time points,
optionally you
can keep them also for point in time recovery;
Then you always have all the WAL files you need to recover to any
point
in time you need. You can then supply all the WAL files which are
needed
by the last file system backup to recover after a crash, or you can
supply all the WAL files up to the time point just before your
student
DBA deleted all your data.
HTH,
Csaba.
On Thu, 2006-01-26 at 18:33, Rick Gigger wrote:
I am looking into using WAL archiving for incremental backups. It
all seems fairly straightforward except for one thing.
So you set up the archiving of the WAL files. Then you set up cron
or something to regularly do a physical backup of the data
directory. But when you do the physical backup you don't have the
last WAL file archived yet that you need to restore that physical
backup. So you always need to keep at least two physical backups
around so that you know that at least one of them has the WAL files
needed for recovery.
The question I have is: how do I know if I can use the latest one?
That is if I first do physical backup A and then later do physical
backup B and then I want to do a restore. How do I know when I've
got the files I need to use B so that I don't have to go all the
way
back to A?
My initial thoughts are that I could:
a) just before or after calling pg_stop_backup check the file
system
to see what the last archived WAL file is on disk and make sure
that
that I get the next one before I try restoring from that backup.
b) just before or after calling pg_stop_backup check postgres to
see
to see what the current active WAL file is and make sure it has
been
archived before I try to restore from that backup.
c) Always just use backup A.
No c seems the easiest but is that even fail safe? I realize it
wouldn't really ever happen in an active production environment
that
was set up right but say you did backup A and backup B and during
that whole time you had few writes in postgres that you never
filled
up a whole WAL file so both of the backups are invalid. Then you
would have to always go to option a or b above to verify that a
given
backup was good so that any previous backups could be deleted.
Wouldn't it make things a lot easier if the backup history file not
only gave you the name of the first file that you need but also the
last one? Then you could look at a given backup and say I need
this
start file and this end file. Then you could delete all
archived WAL
files before start file. And you could delete any old physical
dumps
because you know that your last physical dump was good. It would
just save you the step in the backups process of figuring out what
that file is. And it seems like pg_stop_backup could determine
that
on it's own.
Does that make sense? Am I totally off base here?
Rick
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