Re: Enabling Checksums

2013/3/18 Bruce Momjian <bruce(at)momjian(dot)us>:
> 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, I am unclear who would enable this at
> initdb time.

everybody who has no 100% loaded server.

I can see on almost all PostgreSQL instances load to 5 on 8CPU core instances.

It is similar to PostgreSQL statistics - I remember so it did 20% slowdown too

Regards

Pavel

>
> 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.
>
> pg_upgrade can't handle this because the old/new clusters would have the
> same catalog version number and the tablespace directory names would
> conflict. Even if they are not using tablespaces, the old heap/index
> files would not have checksums and therefore would throw an error as
> soon as you accessed them. 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.
>
> --
> Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
> EnterpriseDB http://enterprisedb.com
>
> + It's impossible for everything to be true. +
>
>
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