Thread: Replication documentation addition
Here is a new replication documentation section I want to add for 8.2:
ftp://momjian.us/pub/postgresql/mypatches/replication
Comments welcomed.
--
Bruce Momjian bruce@momjian.us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
Hello Bruce, Bruce Momjian wrote: > Here is a new replication documentation section I want to add for 8.2: > > ftp://momjian.us/pub/postgresql/mypatches/replication > > Comments welcomed. Thank you, that sounds good. It's targeted to production use and currently available solutions, which makes sense in the official manual. You are explaining the sync vs. async categorization, but I sort of asked myself where the explanation of single vs multi-master has gone. I then realized, that you are talking about read-only and a "read/write mix of servers". Then again, you are mentioning 'Multi-Master Replication' as one type of replication solutions. I think we should be consistent in our naming. As Single- and Multi-Master are the more common terms among database replication experts, I'd recommend to use them and explain what they mean instead of introducing new names. Along with that, I'd argue that this Single- or Multi-Master is a categorization as Sync vs Async. In that sense, the last chapter should probably be named 'Distributed-Shared-Memory Replication' or something like that instead of 'Multi-Master Replication', because as we know, there are several ways of doing Multi-Master Replication (Slony-II / Postgres-R, Distributed Shared Memory, 2PC in application code or the above mentioned 'Query Broadcast Replication', which would fall into a Multi-Master Replication model as well) Also in the last chapter, instead of just saying that "PostgreSQL does not offer this type of replication", we could probably say that different projects are trying to come up with better replication solutions. And there are several proprietary products based on PostgreSQL which do solve some kinds of Multi-Master Replication. Not that I want to advertise for any of them, but it just sounds better than the current "no, we don't offer that". As this documentation mainly covers production-quality solutions (which is absolutely perfect), can we document the status of current projects somewhere, probably in a wiki? Or at least mention them somewhere and point to their websites? It would help to get rid of all those rumors and uncertainties. Or are those intentional? Just my two cents. Regards Markus
Hannu Krosing wrote: > I think the "official" term for this kind of "replication" is > Shared-Nothing Clustering. Well, that's just another distinction for clusters. Most of the time it's between Shared-Disk vs. Shared-Nothing. You could also see the very Big Irons as a Shared-Everything Cluster. While it's certainly true, that any kind of data partitioning for databases only make sense for Shared-Nothing Clusters, I don't think it's a 'kind of replication'. AFAIK most database replication solutions are built for Shared-Nothing Clusters. (With the exception of PgCluster-II, I think). Regards Markus
On Tue, 2006-10-24 at 00:20 -0400, Bruce Momjian wrote: > Here is a new replication documentation section I want to add for 8.2: > > ftp://momjian.us/pub/postgresql/mypatches/replication > > Comments welcomed. It's a very good start to a complete minefield of competing solutions. My first thought would be to differentiate between clustering and replication, which will bring out many differences. My second thought would be to differentiate between load balancing, multi-threading, parallel query, high availability and recoverability, which would probably sort out the true differences in the above mix. But that wouldn't help most people and almost everybody would find fault. IMHO most people I've spoken to take "replication" to mean an HA solution, so perhaps we should cover it in those terms. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com
I have changed the text to reference "fail over" and "load balancing". I think it makes it clearer. Let me know what you think. I am hesitant to mention commercial PostgreSQL products in our documentation. --------------------------------------------------------------------------- Markus Schiltknecht wrote: > Hello Bruce, > > Bruce Momjian wrote: > > Here is a new replication documentation section I want to add for 8.2: > > > > ftp://momjian.us/pub/postgresql/mypatches/replication > > > > Comments welcomed. > > Thank you, that sounds good. It's targeted to production use and > currently available solutions, which makes sense in the official manual. > > You are explaining the sync vs. async categorization, but I sort of > asked myself where the explanation of single vs multi-master has gone. I > then realized, that you are talking about read-only and a "read/write > mix of servers". Then again, you are mentioning 'Multi-Master > Replication' as one type of replication solutions. I think we should be > consistent in our naming. As Single- and Multi-Master are the more > common terms among database replication experts, I'd recommend to use > them and explain what they mean instead of introducing new names. > > Along with that, I'd argue that this Single- or Multi-Master is a > categorization as Sync vs Async. In that sense, the last chapter should > probably be named 'Distributed-Shared-Memory Replication' or something > like that instead of 'Multi-Master Replication', because as we know, > there are several ways of doing Multi-Master Replication (Slony-II / > Postgres-R, Distributed Shared Memory, 2PC in application code or the > above mentioned 'Query Broadcast Replication', which would fall into a > Multi-Master Replication model as well) > > Also in the last chapter, instead of just saying that "PostgreSQL does > not offer this type of replication", we could probably say that > different projects are trying to come up with better replication > solutions. And there are several proprietary products based on > PostgreSQL which do solve some kinds of Multi-Master Replication. Not > that I want to advertise for any of them, but it just sounds better than > the current "no, we don't offer that". > > As this documentation mainly covers production-quality solutions (which > is absolutely perfect), can we document the status of current projects > somewhere, probably in a wiki? Or at least mention them somewhere and > point to their websites? It would help to get rid of all those rumors > and uncertainties. Or are those intentional? > > Just my two cents. > > Regards > > Markus > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
Simon Riggs wrote: > On Tue, 2006-10-24 at 00:20 -0400, Bruce Momjian wrote: > > Here is a new replication documentation section I want to add for 8.2: > > > > ftp://momjian.us/pub/postgresql/mypatches/replication > > > > Comments welcomed. > > It's a very good start to a complete minefield of competing solutions. > > My first thought would be to differentiate between clustering and > replication, which will bring out many differences. I have gone with "fail-over" and "load balancing" in the updated text. > My second thought would be to differentiate between load balancing, > multi-threading, parallel query, high availability and recoverability, > which would probably sort out the true differences in the above mix. But > that wouldn't help most people and almost everybody would find fault. Yep. > IMHO most people I've spoken to take "replication" to mean an HA > solution, so perhaps we should cover it in those terms. Yes, I removed any reference to replication. It seemed too general. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +