| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, jd(at)commandprompt(dot)com, Thom Brown <thom(at)linux(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Dave Page <dpage(at)pgadmin(dot)org>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Configuring synchronous replication |
| Date: | 2010-09-23 22:11:43 |
| Message-ID: | 1285279903.17321.1221.camel@ebony |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-committers pgsql-hackers |
On Thu, 2010-09-23 at 20:42 +0300, Heikki Linnakangas wrote:
> If you want the behavior where the master doesn't acknowledge a
> commit
> to the client until the standby (or all standbys, or one of them
> etc.)
> acknowledges it, even if the standby is not currently connected, the
> master needs to know what standby servers exist. *That's* why
> synchronous replication needs a list of standby servers in the master.
>
> If you're willing to downgrade to a mode where commit waits for
> acknowledgment only from servers that are currently connected, then
> you don't need any new configuration files.
As I keep pointing out, waiting for an acknowledgement from something
that isn't there might just take a while. The only guarantee that
provides is that you will wait a long time. Is my data more safe? No.
To get zero data loss *and* continuous availability, you need two
standbys offering sync rep and reply-to-first behaviour. You don't need
standby registration to achieve that.
> But that's not what I call synchronous replication, it doesn't give
> you the guarantees that
> textbook synchronous replication does.
Which textbook?
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Training and Services
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Robert Haas | 2010-09-24 02:09:13 | pgsql: Add contrib/xml2/pgxml.sql to .gitignore |
| Previous Message | Robert Haas | 2010-09-23 21:47:43 | pgsql: Replace doc references to install-win32 with install-windows. |
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Kevin Grittner | 2010-09-23 23:58:40 | Re: .gitignore files, take two |
| Previous Message | Tom Lane | 2010-09-23 22:04:58 | Re: git cherry-pick timestamping issue |