Thread: "stopping" a single database in a cluster

Hi,
Is it possible to stop a single database, like it is with Oracle? Our
oracle admin asked this for FS backups, if there are 3 dbs (in
separate tablespaces) then there seems no reason why this couldn't be
possible... is it possible?
Cheers
Antoine
ps. If this isn't possible, what experiences do people have with
running several postgres instances on a single machine?

Anton Melser wrote:
> Hi,
> Is it possible to stop a single database, like it is with Oracle? Our
> oracle admin asked this for FS backups, if there are 3 dbs (in
> separate tablespaces) then there seems no reason why this couldn't be
> possible... is it possible?

No - the transaction log (WAL) is shared. You'll need to include that in
any filesystem backup.

> ps. If this isn't possible, what experiences do people have with
> running several postgres instances on a single machine?

It's perfectly possible - most of the developers do so, and I do it so I
can test new versions while supporting old ones. Of course, each will
have their own shared memory allocations so that might impact your
performance.

--
   Richard Huxton
   Archonet Ltd

> Is it possible to stop a single database, like it is with Oracle? Our
> oracle admin asked this for FS backups, if there are 3 dbs (in
> separate tablespaces) then there seems no reason why this couldn't be
> possible... is it possible?

No, this is not possible, because they are all serverd by the same
server process.
You can, however, do an online backup while the database is running.
This is essentially a filesystem backup, and you issue a certain
SQL statement before and after the backup.

> ps. If this isn't possible, what experiences do people have with
> running several postgres instances on a single machine?

It is called 'cluster', not 'instance'.
I have very good experiences.

Yours,
Laurenz Albe