Re: Two instances of Postgres with single data directory

On 11/14/2014 2:24 AM, Albe Laurenz wrote:
> dineshkaarthick wrote:
>> >I would like to know how is the "Shared Disk Failover" replication achieved
>> >if it is not possible to share the data directory ? I am referring to the
>> >1st solution in the mentioned link,
>> >http://www.postgresql.org/docs/9.3/static/different-replication-solutions.html
> You have some cluster software that makes dead sure that one node is*not*
> running the database server before starting it on the other.

more specifically, that the data volume isn't even MOUNTED by the other
server. typically this is enforced with hardware 'fencing' such that
the standby server is blocked from even trying to mount the shared
volume, until it decides to take over, then it fences the original
'master', unfences itself, and mounts the volume, then starts its copy
of postgresql. this fencing is often done in a storage switch
(fiberchannel most commonly).

--
john r pierce 37N 122W
somewhere on the middle of the left coast