We are trying to achieve High Availability over load balancing, so basically we always try and have 2 databases in the same state while both are active, and if one goes down it should (hopefully) failover seemlessly. Thanks for the info on OpenSSI, as i had not heard of this before and will look into it further.
Cheers, Andy On 26/12/06, Shoaib Mir <[EMAIL PROTECTED]> wrote:
Why are you going for a multimaster case here? are you doing it for load balancing? if then you can also do it horizontally with a multi disk setup... Slony can be a real good candidate here as well with Linux HA in combination. For going on a vertical solution you can try OpenSSI and see if that can work for you, haven't tried that myself but will like to hear about PostgreSQL configuration with OpenSSI ------------------- Shoaib Mir EnterpriseDB ( www.enterprisedb.com) On 12/26/06, Andy Dale <[EMAIL PROTECTED]> wrote: > > The company i am working for has a trail/evaluation license for > p/cluster, but unfortunately i cannot get it to function as a JBoss > datasource. > > Cheers, > > Andy > > On 26/12/06, Shoaib Mir <[EMAIL PROTECTED]> wrote: > > > > Yes, that is true with pgpool. I did face the same as well. > > > > There is another as well Uni-Cluster (http://www.continuent.com/index.php?option=com_content&task=view&id=213&Itemid=170 > > ), haven't tried yet but it might help you there... > > > > --------------- > > Shoaib Mir > > EnterpriseDB ( www.enterprisedb.com) > > > > On 12/26/06, Andy Dale <[EMAIL PROTECTED]> wrote: > > > > > > The issue i had with pgpool (1 or 2) was that (correct me if i am > > > wrong) you had to start the pgpool cluster with both nodes in the same > > > state. I thought this would mean that if you had a DB fail, before you > > > could re-introduce it into the pgpool cluster you would have to manually > > > sync it with the cluster state, is this correct ?? > > > > > > The system i need multi master sync for is highly transactional, so > > > if the behaviour i stated above is correct it is not suitable. I have tried > > > s-lony, and while i was pleased with the performance, it is only Single > > > Master - Multi Slave which is not acceptable as well. > > > > > > Andy > > > > > > On 26/12/06, Shoaib Mir <[EMAIL PROTECTED] > wrote: > > > > > > > > pgpool-II might help you there too I guess... > > > > > > > > --------------- > > > > Shoaib Mir > > > > EnterpriseDB ( www.enterprisedb.com) > > > > > > > > On 12/26/06, Andy Dale <[EMAIL PROTECTED]> wrote: > > > > > > > > > > Hi, > > > > > > > > > > I have just read the statement that Postgres does have (with end > > > > > user assembly) multi-master replication system. Is this just PGCluster or > > > > > something else ? if it is not PGCluster, then how can this be achieved ? > > > > > > > > > > Cheers, > > > > > > > > > > Andy > > > > > > > > > > On 24/12/06, Shoaib Mir < [EMAIL PROTECTED]> wrote: > > > > > > > > > > > > I guess the latest 8.2 Windows PostgreSQL installer does come > > > > > > with a Slony option and you can set it up easily using pgadmin too. > > > > > > > > > > > > This link --> > > > > > > http://people.planetpostgresql.org/xzilla/index.php?/archives/200-Alpha-testing-Slony-on-win32-Crib-Notes.htmlmight help you as well. > > > > > > > > > > > > ----------------- > > > > > > Shoaib Mir > > > > > > EnterpriseDB (www.enterprisedb.com) > > > > > > > > > > > > On 12/25/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > > > > > > > > > > > > Thanks Chris, > > > > > > > I see you a core member of Slony team and a replication guru > > > > > > > so I'll look > > > > > > > into it. > > > > > > > I'm not slamming Slony I think its probably the right tool > > > > > > > for type of work > > > > > > > your company Afilias does. Just wish you would make an > > > > > > > official Windows > > > > > > > version of Slony as well. > > > > > > > Anyway thanks for the education, and I think it would be a > > > > > > > good thing if > > > > > > > your site on replication, was also listed on Postgresql... > > > > > > > good research. > > > > > > > Merry Xmas > > > > > > > > > > > > > > ----- Original Message ----- > > > > > > > From: "Christopher Browne" <[EMAIL PROTECTED]> > > > > > > > To: < pgsql-general@postgresql.org> > > > > > > > Sent: Sunday, December 24, 2006 4:23 AM > > > > > > > Subject: Re: [GENERAL] Clustering & Load Balancing & > > > > > > > Replication > > > > > > > > > > > > > > > > > > > > > > Centuries ago, Nostradamus foresaw when > > > > > > > [EMAIL PROTECTED] would write: > > > > > > > >> Suggest you download my little application and read the > > > > > > > documentation, > > > > > > > >> you'll see its very different, maybe even interesting. > > > > > > > >> Maybe they should change that to.... Postgres DOES HAVE a > > > > > > > free > > > > > > > >> multi-master > > > > > > > >> replication system :) > > > > > > > > > > > > > > > > It isn't systematically usable as such, without a whole > > > > > > > lot of > > > > > > > > end-user assembly. > > > > > > > > > > > > > > > >> One comment they make.... "Heavy write activity can cause > > > > > > > excessive > > > > > > > >> locking, > > > > > > > >> leading to poor performance. In fact, write performance > > > > > > > is often worse > > > > > > > >> than > > > > > > > >> that of a single server. Read requests can be sent to any > > > > > > > server." > > > > > > > >> I'm not sure I agree with that... or maybe MVCC is just > > > > > > > fantastic.... I > > > > > > > >> tested it. > > > > > > > >> The 2 phase commit locking is definitely happening at > > > > > > > record level, so > > > > > > > >> only > > > > > > > >> if the multimasters all hit the same record is there the > > > > > > > potential for > > > > > > > >> lock > > > > > > > >> conflict. > > > > > > > >> Why will dB's being randomly used, hit the same records, > > > > > > > I think its a > > > > > > > >> low > > > > > > > >> probability to begin with? > > > > > > > > > > > > > > > > That's only true if you are certain that the update > > > > > > > pattern is NOT > > > > > > > > involving a shared set of records. IN GENERAL, heavy > > > > > > > write activity > > > > > > > > can cause locking to become mighty expensive, which is > > > > > > > certainly a > > > > > > > > true statement. > > > > > > > > > > > > > > > >> Not happy with that, I wrote a multithreaded routine and > > > > > > > got them to all > > > > > > > >> smack the same record, it NEVER ROLLED BACK, and if there > > > > > > > is performance > > > > > > > >> degradation, I didnt notice it... again probably a > > > > > > > testament to the MVCC > > > > > > > >> design. > > > > > > > > > > > > > > > > It seems likely to me that this requires some careful > > > > > > > validation of > > > > > > > > testing. > > > > > > > > > > > > > > > > An effect we see is that if a set of transactions are > > > > > > > "fighting" over > > > > > > > > a single "balance" record, they will essentially serialize > > > > > > > over that. > > > > > > > > > > > > > > > > On a system with a single CPU, it is not obvious that > > > > > > > you'll see a > > > > > > > > degradation there because, since you only have the single > > > > > > > CPU, it > > > > > > > > would be serializing the activity anyways. > > > > > > > > > > > > > > > > Try it out on an 8-way SMP system and you may see things > > > > > > > differently. > > > > > > > > > > > > > > > >> In any event if you look at the documentation, you'll see > > > > > > > SPAR is not > > > > > > > >> multimaster or nothing. Can use say one server in an > > > > > > > office and another > > > > > > > >> to > > > > > > > >> pump data to a remote web site... not sure if you would > > > > > > > even call that > > > > > > > >> multimaster, thats the point, I'm not sure SPAR fits any > > > > > > > pure theory > > > > > > > >> category. > > > > > > > > > > > > > > > > There are a few tests I could throw at it that tend to > > > > > > > challenge > > > > > > > > replication systems vis-a-vis "fidelity of results." I > > > > > > > otta see if I > > > > > > > > can find them in a readily deployable form. > > > > > > > > > > > > > > > > There are two notable anomalies which have been known to > > > > > > > break > > > > > > > > replication systems: > > > > > > > > > > > > > > > > 1. Nondeterministic updates: > > > > > > > > > > > > > > > > For instance, functions that are nondeterministic: > > > > > > > > > > > > > > > > insert into rtable values (random(), now()); > > > > > > > > > > > > > > > > Or result sets that are nondeterministic: > > > > > > > > > > > > > > > > insert into rtable2 (select * from mytable where > > > > > > > some_attr='foo' > > > > > > > > order by random() limit 5); -- Where there are 25 > > > > > > > records with > > > > > > > > some_attr='foo' > > > > > > > > > > > > > > > > 2. Value swapping: > > > > > > > > > > > > > > > > Consider the table: > > > > > > > > > > > > > > > > create table t1 (mk integer primary key, val text unique > > > > > > > not null); > > > > > > > > > > > > > > > > insert into t1 (mk, val) values (1, 'chris'); > > > > > > > > insert into t1 (mk, val) values (2, 'dave'); > > > > > > > > insert into t1 (mk, val) values (3, 'brad'); > > > > > > > > > > > > > > > > begin; > > > > > > > > update t1 set mk = 99 where mk = 1; > > > > > > > > update t1 set mk = 1 where mk = 3; > > > > > > > > update t1 set mk = 3 where mk = 99; > > > > > > > > commit; > > > > > > > > > > > > > > > > Is there a condition where a pause somewhere in there will > > > > > > > cause > > > > > > > > replication to break? Note that there have been > > > > > > > replication systems > > > > > > > > (erServer) that this set of updates can, intermittently, > > > > > > > cause to fall > > > > > > > > over. > > > > > > > > -- > > > > > > > > let name="cbbrowne" and tld=" linuxfinances.info" in > > > > > > > String.concat "@" > > > > > > > > [name;tld];; > > > > > > > > http://cbbrowne.com/info/slony.html > > > > > > > > "Feel free to contact me (flames about my english and > > > > > > > the useless of > > > > > > > > this driver will be redirected to /dev/null, oh no, it's > > > > > > > full...)" > > > > > > > > -- Michael Beck, describing the PC-speaker sound device > > > > > > > > > > > > > > > > ---------------------------(end of > > > > > > > broadcast)--------------------------- > > > > > > > > TIP 2: Don't 'kill -9' the postmaster > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ---------------------------(end of > > > > > > > broadcast)--------------------------- > > > > > > > TIP 5: don't forget to increase your free space map settings > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
