On 10 May 2005, at 15:41, John A Meinel wrote:
Alex Stapleton wrote:
What is the status of Postgres support for any sort of multi-machine
scaling support? What are you meant to do once you've upgraded your box
and tuned the conf files as much as you can? But your query load is
just too high for a single machine?
Upgrading stock Dell boxes (I know we could be using better machines, but I am trying to tackle the real issue) is not a hugely price efficient way of getting extra performance, nor particularly scalable in the long term.
Switch from Dell Xeon boxes, and go to Opterons. :) Seriously, Dell is far away from Big Iron. I don't know what performance you are looking for, but you can easily get into inserting 10M rows/day with quality hardware.
Better hardware = More Efficient != More Scalable
But actually is it your SELECT load that is too high, or your INSERT load, or something inbetween.
Because Slony is around if it is a SELECT problem. http://gborg.postgresql.org/project/slony1/projdisplay.php
Basically, Slony is a Master/Slave replication system. So if you have INSERT going into the Master, you can have as many replicated slaves, which can handle your SELECT load. Slony is an asynchronous replicator, so there is a time delay from the INSERT until it will show up on a slave, but that time could be pretty small.
<snip>
So, when/is PG meant to be getting a decent partitioning system? MySQL
is getting one (eventually) which is apparently meant to be similiar to
Oracle's according to the docs. Clusgres does not appear to be
widely/or at all used, and info on it seems pretty thin on the ground,
so I am
not too keen on going with that. Is the real solution to multi- machine
partitioning (as in, not like MySQLs MERGE tables) on PostgreSQL
actually doing it in our application API? This seems like a less than
perfect solution once we want to add redundancy and things into the mix.
There is also PGCluster http://pgfoundry.org/projects/pgcluster/
Which is trying to be more of a Synchronous multi-master system. I
haven't heard of Clusgres, so I'm guessing it is an older attempt, which
has been overtaken by pgcluster.
Just realize that clusters don't necessarily scale like you would want
them too. Because at some point you have to insert into the same table,
which means you need to hold a lock which prevents the other machine
from doing anything. And with synchronous replication, you have to wait
for all of the machines to get a copy of the data before you can say it
has been committed, which does *not* scale well with the number of machines.
This is why I mention partitioning. It solves this issue by storing different data sets on different machines under the same schema. These seperate chunks of the table can then be replicated as well for data redundancy and so on. MySQL are working on these things, but PG just has a bunch of third party extensions, I wonder why these are not being integrated into the main trunk :/ Thanks for pointing me to PGCluster though. It looks like it should be better than Slony at least.
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