Re: SAN, clustering, MPI, Backplane Re: Postgresql on

Le jeu 08/07/2004 à 14:22, Andrew Piskorski a écrit :
> You want to do clustering for failover/reliability reasons, for
> performance/scalability reasons, or for both?
for all that of course :)

> For some stuff to read, see the dozen or so links I posted here:
>
> http://openacs.org/forums/message-view?message_id=128060
I already see all these one, but thanks :)

> E.g., the Lustre cluster file system claims full POSIX file system
> semantics (locking, etc.), so you should certainly be able to run
> PostgreSQL on it. No idea how well that works, but it should
> certainly let you do fail over.
As a standard filesystem on a SAN configured for take care about
only one node can mount the fs at the same time (using stonith for
example).

> Perhaps you could even somehow, eventually, get multiple PostgreSQL
> instances on different machines to all cooperate with read/write
> access to the same database files over the network. (And without
> using super-expensive SCI hardware the way Clusgres does.) That might
> get you a true cluster RDBMS, if it worked well.
It's exactly what i want.

> Just how closely tied is PostgreSQL to its use of shared memory?
I see very interesting article about openMosix which support clustered
shared memory and distributed locking and processus migration (at OS
level) : http://howto.ipng.be/MigSHM-openMosix/x90.html

Seems the only things which forbid using Postgres with OpenMosix
is the "Actually PostgreSQL uses shared memory but not the system
semaphores for locking it. Thus, it does not satisfy migShm constraints
and so it cannot benefit from migShm."

migShm constraint are here: http://mcaserta.com/maask/assumptions.html

> What about PostgreSQL specifically makes message passing no good, and
> is the same also true for ALL RDBMSs? What about systems like
> Backplane, which claims to be "the only open-source, transactional,
> truly distributed database."?
>
> http://www.backplane.com/
Thanks for this links, since a time i thinked to found exactly
what i'm searching ... Until i read that :

LIMITATIONS
* Only one datatype is implemented, 'varchar'. In otherwords,
everything is a string.
* We do not support triggers
* We do not support UNIQUE
* We only support AND clauses - no parenthesis or OR. Yet.
....

http://www.backplane.com/docs.shtml?doc=2