Re: Hourly backup using pg_basebackup

[John Scalia <jayknowsunix@xxxxxxxxx>]

On 2/6/2015 2:25 PM, Matheus de Oliveira wrote:

On Fri, Feb 6, 2015 at 4:53 PM, John Scalia <jayknowsunix@xxxxxxxxx> wrote:

We have a python script called by cron on an hourly basis to back up our production database. Currently, the script invokes pg_dump and takes more than hour to complete. Hence the script looks to see if it's already running and exits if so. I want to change the script so it uses pg_basebackup instead since that's so much faster.

Have you considered using incremental backup (continuous archiving) instead of a such small backup window?

See [1]

My problem is, however, that while I'd like to just have it build a tarball, maybe compressed,  I can't use a "-X s" option for the wal segments. I think I understand why I can't use the streaming option with a "-Ft" specified. I'm just concerned about the docs saying that the backup may have problems with fetch as a wal segment may have expired. Manually testing is showing that the Db needs about 11 minutes to backup with pg_basebackup, and our wal_keep_segments setting is 6.  This said, an hour's worth of wal segments should be available, but the six that were there at the beginning of the backup are not the same six there at the end. I don't think this is really a problem, but I'd like to get it confirmed. Wouldn't the backup actually have to take more than hour for this to be an issue?

If you use archiving [1], you don't need to worry about saving the segments withing the backup, just let it be done through archive_command. Isn't that an option for you? If don't, why?

Oh, yes, I did fail to mention that the system where I'm trying this is the primary in a streaming replication cluster with (2) hot standby servers. I've mentioned without much traction, that we don't really even need a backup with 3 servers ready to do the work without delays. Like I said in the last post, it's all political.

[1] http://www.postgresql.org/docs/current/static/continuous-archiving.html

Best regards,
--

Matheus de Oliveira
Analista de Banco de Dados
Dextra Sistemas - MPS.Br nível F!
www.dextra.com.br/postgres