Re: warm standby - apply wal archives

From: Venkat Balaji <venkat(dot)balaji(at)verse(dot)in>
To: MirrorX <mirrorx(at)gmail(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: warm standby - apply wal archives
Date: 2011-09-19 05:10:54
Message-ID: CAFrxt0g1KQ=LkRFBrt9vSq1Am2yS_XPCpUmAF7V1xOffVE8=Ng@mail.gmail.com
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Syncing just WAL archive directory every minute should not be a problem at
all (running rsync every minute for a data directory is not recommended).

As said earlier, we had configured warm standby for a db of size 2 TB and
wal archive generation was in 100s.

We did not encounter any issues in running an rsync job with a frequency of
even less than a minute. We made sure that
rsync job is running on standby server (we were pulling the wal archives to
standby).

1. compress the wal archives
2. rsync on standby site
3. uncompress on standby site

Thanks
Venkat

On Sat, Sep 17, 2011 at 6:06 PM, MirrorX <mirrorx(at)gmail(dot)com> wrote:

> just another update since the system is up and running and one more
> question
> :p
>
> the secondary server is able to restore the wal archives practically
> immediately after they arrive. i have set a rsync cron job to send the new
> wals every 5 minutes. the procedure to transfer the files and to restore
> them takes about 30 seconds (the number of archives is about 20-30). i ve
> tried to set it to 2 minutes, and then the procedure takes about 20 seconds
> (both transfer and restoration) while i didnt notice any impact on the
> primary server (the procedure is initiated on the secondary server). what
> is
> your opinion about the time interval that the cron job should run? i ve
> read many articles online indicating that rsync should not run every 1
> minute, but in my case isn't it different since it just syncs two folder
> containing only wals and not the whole disks? plus both folders on the
> servers are in different partitions.
> thx in advance for your insight
>
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