| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, david(at)fetter(dot)org, aidan(at)highrise(dot)ca, stark(at)mit(dot)edu, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: 16-bit page checksums for 9.2 |
| Date: | 2012-01-07 10:14:30 |
| Message-ID: | CA+U5nMKRjLgogD=BihP5jnuhmOAbU_y_ZZr5z+xELzXJQQ8xRw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Jan 6, 2012 at 9:44 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> Writing pages during recovery doesn't need WAL. If we crash, we replay
>> using the already generated WAL.
>
> Which is all fine, except when you start making changes that are not
> WAL-logged. Then, you have the same torn page problem that exists
> when you it in normal running.
Yes, of course. My point is that this is not a blocker to using
checksums, only that some actions cannot occur on the standby but the
replay of changes is not in danger.
page_checksums is an optional parameter, so you can turn it on or off
on the standby as you wish. People frequently have a standby dedicated
to HA and other standbys for queries. So this is all normal and
natural.
page_checksums will default to 'off' in the final patch anyway, in my
understanding.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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