Thread: Two instances of Postgres with single data directory
All, I need to know is it possible to execute two instances of Postgres with single data directory shared between the two instances. This is to know if we can achieve Oracle RAC like cluster for Postgres. Regards Dina -- View this message in context: http://postgresql.nabble.com/Two-instances-of-Postgres-with-single-data-directory-tp5826788.html Sent from the PostgreSQL - general mailing list archive at Nabble.com.
On Thu, Nov 13, 2014 at 9:17 PM, dineshkaarthick <dineshkaarthick@yahoo.co.uk> wrote: > All, > > I need to know is it possible to execute two instances of Postgres with > single data directory shared between the two instances. No, a server instance cannot run on a data folder being used by an existing instance. -- Michael
Michael, Appreciate your quick response. Thank you. 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 Regards Dina -- View this message in context: http://postgresql.nabble.com/Two-instances-of-Postgres-with-single-data-directory-tp5826788p5826972.html Sent from the PostgreSQL - general mailing list archive at Nabble.com.
Hi, On Fri, 2014-11-14 at 02:57 -0700, 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 It is not a replication -- it is HA solution. That particular one can be used along with Red Hat Cluster Suite (now called Red Hat High Availability Addon). A presentation is here: http://www.gunduz.org/download.php?dlid=208 Regards, -- Devrim GÜNDÜZ Principal Systems Engineer @ EnterpriseDB: http://www.enterprisedb.com PostgreSQL Danışmanı/Consultant, Red Hat Certified Engineer Twitter: @DevrimGunduz , @DevrimGunduzTR
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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. Yours, Laurenz Albe
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.htmlYou 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