Re: High Availability: Hot Standby vs. Warm Standby

On Fri, Jul 9, 2010 at 4:51 AM, Thomas Kellerer <spam_eater(at)gmx(dot)net> wrote:
> Hi,
>
> we are contemplating the possibilities for a Postgres HA installation.
>
> As the rollout is targeted towards the end of the year, 9.0 and it's new
> features might be an option for us.
>
> Now from a HA point of view, what is the major difference between 9.0's Hot
> Standby and 8.x's Warm Standby?

You can run queries on the standby...
>
> I am aware that I can use the 9.0 standby server for read only queries, but
> that is (currently) not something we need
>

Taking SQL backups without impacting the master might be something to consider.

> I'm wondering about the differences when the failover situation occurs. From
> reading the docs, I get the impression that 9.0's streaming replication
> might be faster than 8.4's WAL shipping, but otherwise offers the same level
> of data protection.
>
> Is there a difference in how much data could potentially be lost in case of
> a failover?

9.0 has streaming replication so much less data would likely be lost.
WAL logs are generally 16 MB and often shipped when completed.

> E.g. because 9.0 replicates the changes quicker than 8.4?
>
> If there is no (big) difference in reliability (or potential data loss) I
> would rather go for 8.4 than 9.0 just because the feature is so new in 9.0
> and might not be 100% reliable at the beginning.
>
> Any input is highly appreciated.
>
> Thanks in advance
> Thomas
>
>
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--
Rob Wultsch
wultsch(at)gmail(dot)com