Re: Starting new cluster from base backup

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От Guillaume Drolet
Тема Re: Starting new cluster from base backup
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Msg-id CAOkiyv486WqjYxXaRH_k6X4p7f2m+jf8FsQ2JFPa560x2Vp_RA@mail.gmail.com
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Ответ на Re: Starting new cluster from base backup  (Adrian Klaver <adrian.klaver@aklaver.com>)
Ответы Re: Starting new cluster from base backup  (Adrian Klaver <adrian.klaver@aklaver.com>)
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2015-02-18 16:11 GMT-05:00 Adrian Klaver <adrian.klaver@aklaver.com>:
On 02/18/2015 11:51 AM, Guillaume Drolet wrote:


2015-02-18 13:40 GMT-05:00 Adrian Klaver <adrian.klaver@aklaver.com
<mailto:adrian.klaver@aklaver.com>>:

    On 02/18/2015 10:24 AM, Guillaume Drolet wrote:



        2015-02-18 11:06 GMT-05:00 Adrian Klaver
        <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
        <mailto:adrian.klaver@aklaver.__com
        <mailto:adrian.klaver@aklaver.com>>>:



             So is E:\ a network drive shared by both machines?


        No, E:\ is a local drive on which I created a tablespace, in
        order to
        have enough space for my database. In my current setup on the source
        machine, PGDATA is in the default PGSQL installation on the OS
        disk so
        space is limited. On the destination machine, PGDATA will be on a
        different, larger disk than the OS disk.


    So is there an E:\ drive available on the destination machine?


Yes there is an E:\ drive available on the destination machine. But for
now, these two machines don't communicate. I take the backup on a hot
swap disk (F:\) and then swap it into the destination machine.
Ultimately when my database will be running on the destination machine,
I'll connect to it from other machines in my local network.

So if I understand correctly you have:

1) On source machine a directory E:\Data\Database.
2) On the source machine in Postgres you have a created a tablespace that points at E:\Data\Database.
3) On destination machine you have an E:\ drive also.

You're correct
 
Then have you tried:

1) Create \Data\Database directory under E:\ on the destination machine.
2) Do the pg_basebackup.

I'm not sure I understand why, at this moment in the sequence of operation, I would create \Data\Database under E:\ on the destination machine.
pg_basebackup, when run on the source DB on the source machine, has no idea about the destination machine. Maybe you're confused with the F:\ drive, which is the drive on which I tried to save my base backup with the command:

pg_basebackup -D "F:\208376PT\db" -X stream -l "208376PT17022015" -U postgres -P

This drive (F:\) is not the destination machine, it's a swappable disk I use to move my base backup from one machine (the source) to another (the destination).
 


Can't the dependency issue be fixed by creating a new junction in
data/pg_tblspc that would point to the relocated tablespace?

The docs say you can:

http://www.postgresql.org/docs/9.3/static/manage-ag-tablespaces.html

"The directory $PGDATA/pg_tblspc contains symbolic links that point to each of the non-built-in tablespaces defined in the cluster. Although not recommended, it is possible to adjust the tablespace layout by hand by redefining these links. Under no circumstances perform this operation while the server is running. Note that in PostgreSQL 9.1 and earlier you will also need to update the pg_tablespace catalog with the new locations. (If you do not, pg_dump will continue to output the old tablespace locations.)"


I have not done it and I see the "Although not recommended.." part above, so I would say that is a last resort solution.

I confirm this method works. I've done it in the past using the steps in this blog and its comments:

http://www.databasesoup.com/2013/11/moving-tablespaces.html












                          Thanks.



--
Adrian Klaver
adrian.klaver@aklaver.com

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