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Hot standby documentation
Having concluded I really need to start playing with hot standby, I started looking for documentation on the subject. I found what I was looking for; I also found this page[1], which, it seems, ought to mention hot standby. Comments? [1] http://developer.postgresql.org/pgdocs/postgres/high-availability.html -- Joshua Tolley / eggyknap End Point Corporation http://www.endpoint.com
On Thu, Jan 7, 2010 at 6:09 PM, Joshua Tolley <eggyknap(at)gmail(dot)com> wrote: > Having concluded I really need to start playing with hot standby, I started > looking for documentation on the subject. I found what I was looking for; I > also found this page[1], which, it seems, ought to mention hot standby. > Comments? > > [1] http://developer.postgresql.org/pgdocs/postgres/high-availability.html +1 At least, it should be mentioned that the slave can answer read-only queries in "Warm Standby Using Point-In-Time Recovery". And so "Table 25-1" should be changed. Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center
On Thu, 2010-01-07 at 18:34 +0900, Fujii Masao wrote: > On Thu, Jan 7, 2010 at 6:09 PM, Joshua Tolley <eggyknap(at)gmail(dot)com> wrote: > > Having concluded I really need to start playing with hot standby, I started > > looking for documentation on the subject. I found what I was looking for; I > > also found this page[1], which, it seems, ought to mention hot standby. > > Comments? > > > > [1] http://developer.postgresql.org/pgdocs/postgres/high-availability.html > > +1 > > At least, it should be mentioned that the slave can answer > read-only queries in "Warm Standby Using Point-In-Time Recovery". > And so "Table 25-1" should be changed. OK, will add. -- Simon Riggs www.2ndQuadrant.com
Joshua Tolley wrote: -- Start of PGP signed section. > Having concluded I really need to start playing with hot standby, I started > looking for documentation on the subject. I found what I was looking for; I > also found this page[1], which, it seems, ought to mention hot standby. > Comments? > > [1] http://developer.postgresql.org/pgdocs/postgres/high-availability.html Ah, I now realize it only mentions "warm" standby, not "hot", so I just updated the documentation to reflect that; you can see it here: http://momjian.us/tmp/pgsql/high-availability.html Warm and Hot Standby Using Point-In-Time Recovery (PITR) Do we want to call the feature "hot standby"? Is a read-only standby a "standby" or a "slave"? -- Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
Bruce, Bruce Momjian wrote: > Ah, I now realize it only mentions "warm" standby, not "hot", so I just > updated the documentation to reflect that; you can see it here: Maybe the table below also needs an update, because unlike "Warm Standby using PITR", a hot standby accepts read-only queries and can be configured to not loose data on master failure. > Do we want to call the feature "hot standby"? Is a read-only standby a > "standby" or a "slave"? I think hot standby is pretty much the term, now. Regards Markus Wanner
On Sun, Feb 7, 2010 at 4:41 AM, Markus Wanner <markus(at)bluegap(dot)ch> wrote: > Bruce Momjian wrote: >> Do we want to call the feature "hot standby"? Is a read-only standby a >> "standby" or a "slave"? > > I think hot standby is pretty much the term, now. See here for the previous iteration of this discussion: http://archives.postgresql.org/pgsql-hackers/2009-08/msg00870.php I've always thought this feature was misnamed and nothing has happened to change my mind, but it's not clear whether I'm in the majority. ...Robert
> I've always thought this feature was misnamed and nothing has happened > to change my mind, but it's not clear whether I'm in the majority. I'm afraid force of habit is more powerful than correctness on this one. It's going to be HS/SR whether that's perfectly correct or not. --Josh Berkus
On Feb 7, 2010, at 12:35 PM, Josh Berkus wrote: >> I've always thought this feature was misnamed and nothing has happened >> to change my mind, but it's not clear whether I'm in the majority. > > I'm afraid force of habit is more powerful than correctness on this one. > It's going to be HS/SR whether that's perfectly correct or not. What would be correct? I thought HS/SR were pretty correct (as long as no one confuses SR with synchronous replication!). Best, David
Markus Wanner wrote: > Bruce, > > Bruce Momjian wrote: > > Ah, I now realize it only mentions "warm" standby, not "hot", so I just > > updated the documentation to reflect that; you can see it here: > > Maybe the table below also needs an update, because unlike "Warm Standby > using PITR", a hot standby accepts read-only queries and can be > configured to not loose data on master failure. Ahh, good point. I had not considered the table would change. What I did was to mark "Slaves accept read-only queries" as "Hot only". You can see the result here: http://momjian.us/tmp/pgsql/high-availability.html I did not change "Master failure will never lose data" because the 9.0 streaming implementation is not sychronous (see wal_sender_delay in postgresql.conf), and I don't think even setting that to zero makes the operation synchronous. I think we will have to wait for PG 9.1 for _synchronous_ streaming replication. -- Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
On Mon, Feb 8, 2010 at 10:34 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote: > Ahh, good point. I had not considered the table would change. What I > did was to mark "Slaves accept read-only queries" as "Hot only". Can the "warm standby" still reside in v9.0? If not, the mark of "Hot only" seems odd for me. > I did not change "Master failure will never lose data" because the 9.0 > streaming implementation is not sychronous (see wal_sender_delay in > postgresql.conf), and I don't think even setting that to zero makes the > operation synchronous. I think we will have to wait for PG 9.1 for > _synchronous_ streaming replication. You are right. Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center
Fujii Masao wrote: > On Mon, Feb 8, 2010 at 10:34 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote: > > Ahh, good point. ?I had not considered the table would change. ?What I > > did was to mark "Slaves accept read-only queries" as "Hot only". > > Can the "warm standby" still reside in v9.0? If not, the mark of > "Hot only" seems odd for me. Yes, both hot and warm standby is supported in 9.0. -- Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. +