RE: 2 computers 1hd 2 postgres daemons. Is it possib le?

Yeah, I was really just curious if the proposed system was at a system level
or a network level.  Having two physical machines share (at the system i/o
level) a storage unit is something I have never heard of.  Does such a beast
exist?  I assume other RDBMS's use replication to fulfill high-availability
requirements...

jc

-----Original Message-----
From: Tony Simopoulos [mailto:karkalis@earthling.net]
Sent: Monday, October 16, 2000 5:43 PM
To: Clark, Joel
Cc: pgsql-interfaces@postgresql.org
Subject: Re: [INTERFACES] 2 computers 1hd 2 postgres daemons. Is it
possible?


> Through an NFS mount maybe?
without a "distributed lock manager" sharing cannot be done efficiently.
NFS creates problems both desired features of this set-up.

1) High Availability
if the computer that is serving the NFS mount goes down, any other machine
using the "share" goes down as well -- i.e. single-point
of failure

2) Load Balancing
NFS is extremely expensive.  all that would be balanced is the database
logic; in place sorting, connection overheads, etc.
expensive reads and writes will all hit the NFS mounting server -- i.e.
single-threading every query to the disk i/o of one machine.

tonys.

>
> -----Original Message-----
> From: Tony Simopoulos [mailto:karkalis@earthling.net]
> Sent: Monday, October 16, 2000 3:03 PM
> To: Oscar Serrano
> Cc: pgsql-interfaces@postgresql.org
> Subject: Re: [INTERFACES] 2 computers 1hd 2 postgres daemons. Is it
> possible?
>
>
> a redundant, replicated, or parallel system (choose whichever adjective
> befits your desires) is being developed.  check out
> http://www.erserver.com/.
>
> sharing a single disk is an O/S & hardware problem.  what is your intended
> platform?
>
> good luck,
>
> tonys.
>
> ----- Original Message -----
> From: Oscar Serrano <oserra@fondos.net>
> To: Postgres interfaces <pgsql-interfaces@postgresql.org>
> Sent: Monday, October 16, 2000 2:15 PM
> Subject: [INTERFACES] 2 computers 1hd 2 postgres daemons. Is it possible?
>
>
> > Hi men :-)
> > Just one question for those of you who have spent many time with
postgres.
> > I want to create a load balancing and High Availability system with two
> > servers.
> > This two server have a common hard disk: A RAID 5 server connected to
them
> > by the LAN.
> > I have a hardware machine (WSD+ from RADWARE) that manages the load
> > balancing.
> > I want to have, two servers, and two postgres installations, one in each
> > server, but with a  common PGDATA directory in the RAID.
> > So, if one of the servers crashes, people can still get the information
> from
> > the other server.
> > Esentially, what I want is, two postgres (one in each machine) with a
> shared
> > PGDATA directory, and that both postgres can access and do Inserts in
the
> > tables, and when one postgres does an insert, the second sees what the
> first
> > has inserted.
> >
> > Thanks.
> >
> >
> >
>