Re: 1 cluster on several servers - Mailing list pgsql-general
From | Shane Ambler |
---|---|
Subject | Re: 1 cluster on several servers |
Date | |
Msg-id | 47501511.4020507@Sheeky.Biz Whole thread Raw |
In response to | Re: 1 cluster on several servers ("Willy-Bas Loos" <willybas@gmail.com>) |
List | pgsql-general |
Willy-Bas Loos wrote: > I'll take that as a "no". > What i mean is to actually run exactly one cluster (no replicated copy) on > more than one server. Of course, if that were possible, why would people > bother with replication.. What you may be thinking of is having several machines running postgres and reading/writing to the same "shared" filesystem? It's not advisable to try something like that. (as a read only system it may work fine) Each machine should run their own copy of postgres and have their own copy of the data (which also gives you redundancy) to prevent contention and overwriting other servers changes. To do that you use replication of some sort. How you achieve that depends on your needs. Also think that having ten machines reading and writing to the one hard drive (or array of drives) will not help your performance needs in any way. The hard drive is the slowest point of the server, you want to add more drives to multiply the transfer speeds to reach the performance required. Say you have 10,000 clients requesting data. If you had ten machines reading from the same shared drive you wouldn't get better performance than if one machine was accessing the drive alone. If you had ten machines with their own drives and copy of the data then you would be multiplying the amount of data sent out by ten. Slony would be setup with one server that receives the insert and updates and copies them to the other servers that would handle selects from all your clients. I believe that Slony 2 is suppose to handle multiple masters but I don't believe it is available yet. If you want more than one server to respond to insert and updates then maybe PGCluster may be closer to what you are looking for. This is a multi-master setup where each server commits any changes before the transaction is completed. This will give you each machine having identical copies of data to work with. Cybercluster appears to be a branch from PGCluster. Bucardo is a project that has just recently been released to the community. It supports multi-master replication and was developed by a busy online store to meet their needs. There are several commercial options available from many of the companies that also provide postgres support that may fit your needs better. EnterpriseDB, Commandprompt, Pervasive, Cybertec, Greenplum are the first few that come to mind. The real question is what you want to achieve - supporting an extremely high number of client connections? Redundancy to prevent disaster? > I guess it is irrational to suggest that it would be possible, since each > server would at least need to have it's own copy of the DBMS software etc, > or it would cease to be a separate server. > > Maybe "Data Partitioning", as in the documentation link Shane sent, possibly > combined with Slony for the other data per server, would be an option for > me. > > Is there an implementation for this in PostgreSQL? It would have to be > something like pgPool (middleware), because: How would the query know on > which server to put it's data? And i guess i would need some Kerberos-like > implementation for my authentication and authorization... > > cheers, > > WBL > > > On Nov 29, 2007 1:23 PM, Shane Ambler <pgsql@sheeky.biz> wrote: > >> Willy-Bas Loos wrote: >>> Hi, >>> >>> Is it possible to run one PostgreSQL cluster on more than one (hardware) >>> server? >>> >>> WBL >>> >> You would be looking for replication. >> Start with >> http://www.postgresql.org/docs/8.2/interactive/high-availability.html >> to get some idea on what is available for what you wish to achieve. >> Some of the projects that add these features are mentioned. >> >> >> >> >> -- >> >> Shane Ambler >> pgSQL@Sheeky.Biz >> >> Get Sheeky @ http://Sheeky.Biz >> > -- Shane Ambler pgSQL@Sheeky.Biz Get Sheeky @ http://Sheeky.Biz
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