Re: File system level copy

Hao Wang wrote:
>>> I installed PostgresSQL-8.3 on my linux machine.
>>>
>>> The cluster directory is /usr/local/data and I created three
databases
>>> named db1, db2, and db3. db1 is
>>> in the default tablespace 'pg_default'. db2 is in
>>> '/home/tablespace/space1/' and db3 is in
>>> '/home/tablespace/space2/'. I want to copy the cluster directory
and
>>> the db3 tablespace
>>> folder('/home/tablespace/space2/') without stopping the database
>>> server. Then I want to use the
>>> cluster directory and db3's tablespace in another linux machine to
>>> recover 'db3' database. Does this
>>> way work? If not, why?
>>
>> First, you need a correct backup for recovery.
>> Before copying, run pg_start_backup, and pg_stop_backup afterwards.
>>
>> Then you need to have recovery.conf and WAL archives (or be lucky and
all WALs are still in pg_xlog).
>>
>> WAL contains changes to all databases in the cluster, so you cannot
recover only one database, you'll
>> have to recover them all.
>>
>> Read
>>
http://www.postgresql.org/docs/current/static/continuous-archiving.html
>> for background and details.

> This is PITR, right?
> I don't want to use this way because I'm not allowed to change the
configuration
> parameter of database server. I just want to use some whole DB copy to
restore
> db3 in another machine. And I don't want to use pg_dump because I
think db3
> is so large that pg_dump will probably have bad performance.

That's a whole lot of arbitrary restrictions.

If all you want is a copy of the database, pg_dump is what
you should use. Besides, it is the only way to get a copy
of just one database. What's the problem if pg_dump takes
a few hours or days (I don't know how big you DB is)?

A side thought: if the DB is not configured for PITR and
pg_dump takes too long, how do you perform your backups?

Yours,
Laurenz Albe