Thread: Re: [COMMITTERS] pgsql: Remove replicaiton FAQ item.
Marc G. Fournier wrote: > On Tue, 16 Nov 2004, Robert Treat wrote: > > > On Sunday 14 November 2004 16:33, Bruce Momjian wrote: > >> Log Message: > >> ----------- > >> Remove replicaiton FAQ item. > >> > >> Modified Files: > >> -------------- > >> pgsql/doc: > >> FAQ (r1.269 -> r1.270) > >> > >> (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/FAQ.diff?r1=1.269&r2= > >> 1.270) pgsql/doc/src/FAQ: > >> FAQ.html (r1.227 -> r1.228) > >> > >> (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/FAQ.html.diff > >> ?r1=1.227&r2=1.228) > > > > While the answer may have been a little dated, this still seems to be an FAQ. > > Was there a discussion on removing this? If so I'll go read that, but ISTM > > this question should remain. > > agreed, this definitly does fall under a "Very FAQ" kinda thing ... > pointers to the various methods that are currently in use, at a minimum, > would be good ... Yep, big mistake my removing the replication FAQ item. I have re-added a new one: 4.21) What replication solutions are available? Though "replication" is a single term, there are two major replication technologies. Multi-master replication allows read/write queries to be sent to multiple replicated computers. Using this capability has a serious performance impact. Pgcluster is the most popular such solution available for PostgreSQL. Master-slave replication allows a single master to receive read/write queries, with slaves able to accept only read/SELECT queries. The most popular master-slave PostgreSQL replication solution is Slony. There are also commercial and hardware-based replication solutions available. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073
Should the text include a mention of synchronous vs. asynchronous? Or
does master-master imply synchronous?
Regards,
Jeff Davis
On Sun, 2005-04-24 at 08:01 -0400, Bruce Momjian wrote:
> Marc G. Fournier wrote:
> > On Tue, 16 Nov 2004, Robert Treat wrote:
> >
> > > On Sunday 14 November 2004 16:33, Bruce Momjian wrote:
> > >> Log Message:
> > >> -----------
> > >> Remove replicaiton FAQ item.
> > >>
> > >> Modified Files:
> > >> --------------
> > >> pgsql/doc:
> > >> FAQ (r1.269 -> r1.270)
> > >>
> > >> (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/FAQ.diff?r1=1.269&r2=
> > >> 1.270) pgsql/doc/src/FAQ:
> > >> FAQ.html (r1.227 -> r1.228)
> > >>
> > >> (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/FAQ.html.diff
> > >> ?r1=1.227&r2=1.228)
> > >
> > > While the answer may have been a little dated, this still seems to be an FAQ.
> > > Was there a discussion on removing this? If so I'll go read that, but ISTM
> > > this question should remain.
> >
> > agreed, this definitly does fall under a "Very FAQ" kinda thing ...
> > pointers to the various methods that are currently in use, at a minimum,
> > would be good ...
>
> Yep, big mistake my removing the replication FAQ item. I have re-added a
> new one:
>
> 4.21) What replication solutions are available?
>
> Though "replication" is a single term, there are two major replication
> technologies. Multi-master replication allows read/write queries to be
> sent to multiple replicated computers. Using this capability has a
> serious performance impact. Pgcluster is the most popular such solution
> available for PostgreSQL. Master-slave replication allows a single
> master to receive read/write queries, with slaves able to accept only
> read/SELECT queries. The most popular master-slave PostgreSQL
> replication solution is Slony. There are also commercial and
> hardware-based replication solutions available.
>
Jeff Davis wrote: > Should the text include a mention of synchronous vs. asynchronous? Or > does master-master imply synchronous? It shouldn't. It is possible to have synchronous replication without it being master<->master. Sincerely, Joshua D. Drake > > Regards, > Jeff Davis > > On Sun, 2005-04-24 at 08:01 -0400, Bruce Momjian wrote: > >>Marc G. Fournier wrote: >> >>>On Tue, 16 Nov 2004, Robert Treat wrote: >>> >>> >>>>On Sunday 14 November 2004 16:33, Bruce Momjian wrote: >>>> >>>>>Log Message: >>>>>----------- >>>>>Remove replicaiton FAQ item. >>>>> >>>>>Modified Files: >>>>>-------------- >>>>> pgsql/doc: >>>>> FAQ (r1.269 -> r1.270) >>>>> >>>>>(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/FAQ.diff?r1=1.269&r2= >>>>>1.270) pgsql/doc/src/FAQ: >>>>> FAQ.html (r1.227 -> r1.228) >>>>> >>>>>(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/FAQ.html.diff >>>>>?r1=1.227&r2=1.228) >>>> >>>>While the answer may have been a little dated, this still seems to be an FAQ. >>>>Was there a discussion on removing this? If so I'll go read that, but ISTM >>>>this question should remain. >>> >>>agreed, this definitly does fall under a "Very FAQ" kinda thing ... >>>pointers to the various methods that are currently in use, at a minimum, >>>would be good ... >> >>Yep, big mistake my removing the replication FAQ item. I have re-added a >>new one: >> >> 4.21) What replication solutions are available? >> >> Though "replication" is a single term, there are two major replication >> technologies. Multi-master replication allows read/write queries to be >> sent to multiple replicated computers. Using this capability has a >> serious performance impact. Pgcluster is the most popular such solution >> available for PostgreSQL. Master-slave replication allows a single >> master to receive read/write queries, with slaves able to accept only >> read/SELECT queries. The most popular master-slave PostgreSQL >> replication solution is Slony. There are also commercial and >> hardware-based replication solutions available. >> > > > > ---------------------------(end of broadcast)--------------------------- > TIP 8: explain analyze is your friend
Joshua D. Drake wrote: > Jeff Davis wrote: > > Should the text include a mention of synchronous vs. asynchronous? Or > > does master-master imply synchronous? > > It shouldn't. It is possible to have synchronous replication without it > being master<->master. We could mention async vs sync but at the FAQ stage I think the multi-master/master-slave disinction is enough. Let's see what questions we get. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073
Quoting Bruce Momjian <pgman@candle.pha.pa.us>: > Joshua D. Drake wrote: > > Jeff Davis wrote: > > > Should the text include a mention of synchronous vs. > asynchronous? Or > > > does master-master imply synchronous? > > > > It shouldn't. It is possible to have synchronous replication > without it > > being master<->master. > > We could mention async vs sync but at the FAQ stage I think the > multi-master/master-slave disinction is enough. Let's see what > questions > we get. About all you can say is, it is not possible to implement synchronous master-master replication, because of conflict resolution of simultaneous transactions. -- "Dreams come true, not free." -- S.Sondheim, ITW
Mischa Sandberg wrote: > Quoting Bruce Momjian <pgman@candle.pha.pa.us>: > > > Joshua D. Drake wrote: > > > Jeff Davis wrote: > > > > Should the text include a mention of synchronous vs. > > asynchronous? Or > > > > does master-master imply synchronous? > > > > > > It shouldn't. It is possible to have synchronous replication > > without it > > > being master<->master. > > > > We could mention async vs sync but at the FAQ stage I think the > > multi-master/master-slave disinction is enough. Let's see what > > questions > > we get. > > About all you can say is, it is not possible to implement synchronous > master-master replication, because of conflict resolution of > simultaneous transactions. You mean asynchronous master-master? There are some implementations (Sybase?, pgreplicator) that do this and have conflict resolution. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073
Quoting Bruce Momjian <pgman@candle.pha.pa.us>: > Mischa Sandberg wrote: > > About all you can say is, it is not possible to implement > synchronous > > master-master replication, because of conflict resolution of > > simultaneous transactions. > > You mean asynchronous master-master? There are some implementations > (Sybase?, pgreplicator) that do this and have conflict resolution. Forgive my kibitz, then; perhaps my head has been stuck in sand a while. You're right, I forgot about the nicer bits of Sybase RepServer. Synchronous replication was scratched early in the project, because two-phase commit took too long across a dozen db servers. Pgreplicator advertises itself as a "store-and-forward asynch replica (sic) engine." (quoth http://pgreplicator.sourceforge.net/ ) -- "Dreams come true, not free." -- S.Sondheim, ITW
Martha Stewart called it a Good Thing when pgman@candle.pha.pa.us (Bruce Momjian) wrote: > Yep, big mistake my removing the replication FAQ item. I have re-added a > new one: > > 4.21) What replication solutions are available? > > Though "replication" is a single term, there are two major replication > technologies. Multi-master replication allows read/write queries to be > sent to multiple replicated computers. Using this capability has a > serious performance impact. Pgcluster is the most popular such solution > available for PostgreSQL. Master-slave replication allows a single > master to receive read/write queries, with slaves able to accept only > read/SELECT queries. The most popular master-slave PostgreSQL > replication solution is Slony. There are also commercial and > hardware-based replication solutions available. A suggestion for rewording: Though "replication" is a single term, there are a number of approaches and technologies to handle it, and thus, for different purposes, a number of replication systems are available. Master/slave replication allows a single master to receive read/write queries, where slaves can only accept read/SELECT queries. The most popular freely available master-slave PostgreSQL replication solution is Slony-I. Multi-master replication allows read/write queries to be sent to multiple replicated computers. Using this capability generaly has a fairly severe impact on performance due to the need to synchronize changes between servers. Pgcluster is the most popular such solution freely available for PostgreSQL. There are also commercial and hardware-based replication solutions available supporting a variety of replication models. -- (format nil "~S@~S" "cbbrowne" "acm.org") http://linuxdatabases.info/info/slony.html "It can be shown that for any nutty theory, beyond-the-fringe political view or strange religion there exists a proponent on the Net. The proof is left as an exercise for your kill-file." -- Bertil Jonell
OK, updated:
<P>Though "replication" is a single term, there are several technologies
for doing replication, with advantages and disadvantages for each.</P>
<P>Master/slave replication allows a single master to receive read/write
queries, while slaves can only accept read/<SMALL>SELECT</SMALL> queries.
The most popular freely available master-slave PostgreSQL replication
solution is <A href="http://gborg.postgresql.org/project/slony1/projdisplay$
Slony-I</A>.</P>
<P>Multi-master replication allows read/write queries to be sent to
multiple replicated computers. This capability also has a severe
impact on performance due to the need to synchronize changes between
servers. <A href="http://pgfoundry.org/projects/pgcluster/">Pgcluster</a>
is the most popular such solution freely available for PostgreSQL.</P>
<P>There are also commercial and hardware-based replication solutions
available supporting a variety of replication models.</P>
---------------------------------------------------------------------------
Christopher Browne wrote:
> Martha Stewart called it a Good Thing when pgman@candle.pha.pa.us (Bruce Momjian) wrote:
> > Yep, big mistake my removing the replication FAQ item. I have re-added a
> > new one:
> >
> > 4.21) What replication solutions are available?
> >
> > Though "replication" is a single term, there are two major replication
> > technologies. Multi-master replication allows read/write queries to be
> > sent to multiple replicated computers. Using this capability has a
> > serious performance impact. Pgcluster is the most popular such solution
> > available for PostgreSQL. Master-slave replication allows a single
> > master to receive read/write queries, with slaves able to accept only
> > read/SELECT queries. The most popular master-slave PostgreSQL
> > replication solution is Slony. There are also commercial and
> > hardware-based replication solutions available.
>
> A suggestion for rewording:
>
> Though "replication" is a single term, there are a number of
> approaches and technologies to handle it, and thus, for different
> purposes, a number of replication systems are available.
>
> Master/slave replication allows a single master to receive read/write
> queries, where slaves can only accept read/SELECT queries. The most
> popular freely available master-slave PostgreSQL replication solution
> is Slony-I.
>
> Multi-master replication allows read/write queries to be sent to
> multiple replicated computers. Using this capability generaly has a
> fairly severe impact on performance due to the need to synchronize
> changes between servers. Pgcluster is the most popular such solution
> freely available for PostgreSQL.
>
> There are also commercial and hardware-based replication solutions
> available supporting a variety of replication models.
> --
> (format nil "~S@~S" "cbbrowne" "acm.org")
> http://linuxdatabases.info/info/slony.html
> "It can be shown that for any nutty theory, beyond-the-fringe
> political view or strange religion there exists a proponent on the
> Net. The proof is left as an exercise for your kill-file."
> -- Bertil Jonell
>
> ---------------------------(end of broadcast)---------------------------
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>
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>
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073