Deleting WAL archives and pg_xlog when there is not a shared drive

On Tue, Dec 11, 2012 at 9:37 AM, Eng. AlSamman <iyamen@live.com> wrote:

I am trying to implement a high-availability cluster using only two nodes,
without any shared disk storage.

In my implementation, the primary database has continuous archiving set up
to a directory residing on the second node, where the standby database is.
Streaming replication is also established between the two. When failover
occurs, the standby is promoted to primary, and will start its continuous
archiving but now on a directory on the other (former primary) node.

Call the primary node N1 and the standby N2. When N1 fails and N2 is
promoted, can I safely delete the archive logs stored on N2 (which were
archived by N1 when it was primary?)?

You can.

Also, when N1 is started but now it
must become a standby, I run pg_start_backup() on N2, sync the data
directories (except pg_xlog) then pg_stop_backup() on N2.

You must not start N1 before you have done a base backup
(pg_start_backup()/pg_stop_backup()).

Can I safely
delete everything under pg_xlog in N1 BEFORE starting it since anyways they
won't be used (what will be used instead is the archive directory on N1
which is being populated by N2)?

You can delete everything under N1 data directory before making a base backup.

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On Tue, Dec 11, 2012 at 9:37 AM, Eng. AlSamman <iyamen@live.com> wrote:

Hello everyone,

I am trying to implement a high-availability cluster using only two nodes,
without any shared disk storage.

In my implementation, the primary database has continuous archiving set up
to a directory residing on the second node, where the standby database is.
Streaming replication is also established between the two. When failover
occurs, the standby is promoted to primary, and will start its continuous
archiving but now on a directory on the other (former primary) node.

Call the primary node N1 and the standby N2. When N1 fails and N2 is
promoted, can I safely delete the archive logs stored on N2 (which were
archived by N1 when it was primary?)?

That depends on your backup policy. Do you try to maintain some kind
of PITR availability window, or are you solely concerned with hardware
issues and not human error?

In any case, in the middle of an unusual event seems like a poor time
to go around cleaning up only tangentially related things.

Cheers,

Jeff

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Thank you for your input.

Thanks for the input Jeff. The purpose is primarily automating failover (high-availability). There is no intention of using PITR.

We decided to actually keep the WAL logs in the archive directory (until they start to pose a storage problem) and delete what's under pg_xlog (in the situation I already mentioned in my original message).