Re: Enabling Checksums

On 18 March 2013 17:52, Bruce Momjian <bruce@momjian.us> wrote:
> On Sun, Mar 17, 2013 at 05:50:11PM -0700, Greg Smith wrote:
>> As long as the feature is off by default, so that people have to
>> turn it on to hit the biggest changed code paths, the exposure to
>> potential bugs doesn't seem too bad.  New WAL data is no fun, but
>> it's not like this hasn't happened before.
>
> With a potential 10-20% overhead,

... for some workloads.


> I am unclear who would enable this at initdb time.

Anybody that cares a lot about their data.

> I assume a user would wait until they suspected corruption to turn it
> on, and because it is only initdb-enabled, they would have to
> dump/reload their cluster.  The open question is whether this is a
> usable feature as written, or whether we should wait until 9.4.

When two experienced technical users tell us this is important and
that they will use it, we should listen.


> In fact, this feature is going to need
> pg_upgrade changes to detect from pg_controldata that the old/new
> clusters have the same checksum setting.

I don't see any way they can differ.

pg_upgrade and checksums don't mix, in this patch, at least.

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services