Re: question about HA in PG 9.0

Kasia Tuszynska wrote:
>
> The doc is lovely but all of the examples are for linux, has anyone
> tired a Hot Standby streaming scenario on windows? Any issues
> specific to windows? I know that linux and windows environments
> "should" behave the same but actually running in both of those
> environments exposes many differences.
>

As there is a certain amount of helper scripting required to get
Streaming Replication setup, and the usual scripting languages people
tend to write them in (bash, Python, Perl) don't ship with Windows, you
will have a bit of extra work to do here. I'm not aware of any
production-quality setups that have tested the 9.0 implementation under
Windows yet, but the similar hard parts have certainly been done before
with earlier versions.

> I have been reading up on this issue most notably on
> http://wiki.postgresql.org/wiki/Shared_Storage, where the suggestions
> have been gravitating to solutions on the physical level.
>
> Are there any software level solutions? ( I have a feeling that this
> may be a stupid question, but I want to implement this in the cloud,
> and not potentially kill an ami instance)
>

The only way you will implement "Shoot the other node in the head" on
EC2 approaching the same level of reliability a hardware solution
provides is to do just that: don't begin failover to a new node until
you've made sure the unreponsive master has been killed, and its AMI
instance disabled from powering back up again. Automating that is
exactly where I plan to go with redundant EC2 deployments of this type.
But you could do it as part of a manual failover if you had to. You
cannot let the original master touch the shared data store ever again
once it's been taken out of the loop. If your storage is on EBS, I'm
not sure how that handles two attempts to attach a writer to the store,
but you'd want to test that out too.

--
Greg Smith, 2ndQuadrant US greg(at)2ndQuadrant(dot)com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us
Author, "PostgreSQL 9.0 High Performance" Pre-ordering at:
https://www.packtpub.com/postgresql-9-0-high-performance/book