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.

Yours,
Laurenz Albe

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.

-----Original Message-----
From: Albe Laurenz [mailto:laurenz.albe@wien.gv.at]
Sent: Wednesday, November 14, 2012 6:49 PM
To: Wang, Hao; pgsql-general@postgresql.org
Subject: RE: [GENERAL] 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.

Yours,
Laurenz Albe

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

My purpose is not to do backup for my database. I just want to copy the whole db3 database to another machine and restore it. That database could be very large so I think directly copy is more efficient than pg_dump. So I'd like to do some test to see if this way works. If it doesn't work, I will consider to use pg_dump.
Thank you for your feedback.

-----Original Message-----
From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Albe Laurenz
Sent: Thursday, November 15, 2012 4:52 PM
To: Wang, Hao; pgsql-general@postgresql.org
Subject: Re: [GENERAL] 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

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Hao Wang wrote:

My purpose is not to do backup for my database.

I understood that. It was just a side comment.

I just want to copy the whole db3 database to another
machine and restore it. That database could be very large so I think

directly copy is more efficient

than pg_dump. So I'd like to do some test to see if this way works.

If it doesn't work, I will

consider to use pg_dump.

Any attempt to make a file system copy of a live system without
doing PITR will very likely cause data corruption.

You'll have to use pg_dump.

Yours,
Laurenz Albe