Re: PostgreSQL in Cluster

Hi everyone,

Anyone have PostgreSQL running on a cluster?
I'm trying to run on a OpenMosix 2-machine cluster but the processes are not migrating.
All the load is concentrating in one machine.
And, how can I have fail over?

Thank you,

Luiz

On Fri, 27 Feb 2004, Luiz Guilherme Freitas de Paula wrote:

> Hi everyone,
>
> Anyone have PostgreSQL running on a cluster?
> I'm trying to run on a OpenMosix 2-machine cluster but the processes are not migrating.
> All the load is concentrating in one machine.
> And, how can I have fail over?

so far, everyone who's tested postgresql on openmosix has found it to be
quite slow. IT would appear the shared memory is the deal breaker there.

On Friday 27 February 2004 18:31, Luiz Guilherme Freitas de Paula wrote:
> Hi everyone,
>
> Anyone have PostgreSQL running on a cluster?
> I'm trying to run on a OpenMosix 2-machine cluster but the processes are
> not migrating. All the load is concentrating in one machine.

I don't think openmosix allows shared memory to migrate. Since PG uses shared
memory to communicate between backends, this will cause you problems.

> And, how can I have fail over?

More information?

--
Richard Huxton
Archonet Ltd

Is there any way to use PostgreSQL in a cluster configuration or have
redundancy?
How can I have my DB to not stop on hardware failure?

Thank you,

Luiz

> On Friday 27 February 2004 18:31, Luiz Guilherme Freitas de Paula wrote:
> > Hi everyone,
> >
> > Anyone have PostgreSQL running on a cluster?
> > I'm trying to run on a OpenMosix 2-machine cluster but the processes are
> > not migrating. All the load is concentrating in one machine.
>
> I don't think openmosix allows shared memory to migrate. Since PG uses
shared
> memory to communicate between backends, this will cause you problems.
>
> > And, how can I have fail over?
>
> More information?
>
> --
> Richard Huxton
> Archonet Ltd
>
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>

On Friday 27 February 2004 20:13, Luiz Guilherme Freitas de Paula wrote:
> Is there any way to use PostgreSQL in a cluster configuration or have
> redundancy?

Well, you don't say much about your hardware, usage patterns etc. but you
might want look at the various replication options currently available.

There's one in the source distribution: contrib/dbmirror.
Or perhaps erserver/rservimp on gborg.postgresql.org

> How can I have my DB to not stop on hardware failure?

I don't know of anyone doing instant fail-over to a secondary machine. You
might want to consider the following:

1. External, shared RAID drives (note that you *MUST NOT* run two versions of
PG against the same files)
2. Duplicate machines with replication and one of the "heartbeat+failover"
options (free or commercial)
3. Commercial high-availability hardware (I know - too expensive)

Can't say much more without knowing what you want. Whatever path you decide to
take, do a proper risk assessment first and allow time to understand the
systems involved and too proper testing.

--
Richard Huxton
Archonet Ltd

> Is there any way to use PostgreSQL in a cluster configuration or have
> redundancy?
> How can I have my DB to not stop on hardware failure?

You can have a fail-over cluster by having an external disk array
connected to two machines, where machine B is activated, mounts the
disks, and switches off power from machine A if it fails.

Jon

>
> Thank you,
>
> Luiz
>
> > On Friday 27 February 2004 18:31, Luiz Guilherme Freitas de Paula wrote:
> > > Hi everyone,
> > >
> > > Anyone have PostgreSQL running on a cluster?
> > > I'm trying to run on a OpenMosix 2-machine cluster but the processes are
> > > not migrating. All the load is concentrating in one machine.
> >
> > I don't think openmosix allows shared memory to migrate. Since PG uses
> shared
> > memory to communicate between backends, this will cause you problems.
> >
> > > And, how can I have fail over?
> >
> > More information?
> >
> > --
> > Richard Huxton
> > Archonet Ltd
> >
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> > TIP 3: if posting/reading through Usenet, please send an appropriate
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> > message can get through to the mailing list cleanly
> >
>
>
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>
> http://archives.postgresql.org
>

-----Mensagem original-----
De: pgsql-general-owner(at)postgresql(dot)org
[mailto:pgsql-general-owner(at)postgresql(dot)org] Em nome de Luiz Guilherme
Freitas de Paula
Enviada em: sexta-feira, 27 de fevereiro de 2004 17:14
Para: Richard Huxton; pgsql-general(at)postgresql(dot)org
Assunto: Re: [GENERAL] PostgreSQL in Cluster

Is there any way to use PostgreSQL in a cluster configuration or have
redundancy?
How can I have my DB to not stop on hardware failure?

Thank you,

Luiz

> On Friday 27 February 2004 18:31, Luiz Guilherme Freitas de Paula
wrote:
> > Hi everyone,
> >
> > Anyone have PostgreSQL running on a cluster?
> > I'm trying to run on a OpenMosix 2-machine cluster but the processes
are
> > not migrating. All the load is concentrating in one machine.
>
> I don't think openmosix allows shared memory to migrate. Since PG uses
shared
> memory to communicate between backends, this will cause you problems.
>
> > And, how can I have fail over?
>
> More information?
>
> --
> Richard Huxton
> Archonet Ltd
>
> ---------------------------(end of
broadcast)---------------------------
> TIP 3: if posting/reading through Usenet, please send an appropriate
> subscribe-nomail command to majordomo(at)postgresql(dot)org so that
your
> message can get through to the mailing list cleanly
>

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> Hi everyone,
Hello!
>
> Anyone have PostgreSQL running on a cluster?
Yes. Someone :) Me :)
> I'm trying to run on a OpenMosix 2-machine cluster but the processes are
> not migrating.
The solution you are looking for is depending on what you want to get
srom it. I mean even oracle cluster solution do not allow to migrate
updates if while update is going on the hardware fail happend. It
migrate to a second node and all selects are starting from the beginning
and update and inserts are canselled (as far as i know).
So to find a solution you should know:
1. How much time your database could be unavailable (one second per year
or one hour per day)
2. Does your application could recoonect to a database if the problem arise.
3. Does your application is cappable to check data consistancy (after
insert, update whatever if fail happend)
............
1001.
As for me i answerred all that questions and have the following
configuration:
1. Two Intel SRKA4 machines with RAID1 for OS and RAID5 for databasee (i
know that RAID5 is too slow but for me it is just a solution)
2. Bouth computers connected to different power feeders via different UPSs.
3. I have 3 dedicated Gigabit ethernet connections established between
computers for data mirroring and two more for data access from the network.
4. Red Hat Linux8 installed it is a pitty thing because i'm using
FreeBSD on all other servers but DRBD is available only for linux.
5. All disks being mirrored over a network using DRBD software.
All database drives are configured to write data to remote node first
(Protocol C).
6. Hardware being monitored with heartbeat software that is configured
to send beats each second and if 2 heartbeats are missing it consider it
is as hardware mulfunction
7. Postgress migrating from one computer to another in 5 seconds.
8. There is a special daemon that controlls data consistancy.

Best regards,
Anton
> All the load is concentrating in one machine.
> And, how can I have fail over?
>
> Thank you,
>
> Luiz