Re: What is the relationship between checkpoint and wal

Hello:

Thank you all.

I have understood this.

Best Regards

2013/8/31 Kevin Grittner <kgrittn(at)ymail(dot)com>

> 高健 <luckyjackgao(at)gmail(dot)com> wrote:
>
> > So I think that in a mission critical environment, it is not a
> > good choice to turn full_page_writes on.
>
> If full_page_writes is off, your database can be corrupted in the
> event of a crash of the hardware, OS, or VM (for example a power
> failure). The only exception is if your environment somehow
> guarantees that in such failures it is not possible to write part
> of a 4KB write request without the entire 4KB being written. Such
> corruption may be hidden and result in inconsistent or incorrect
> results, without generating an error; so you would be well-advised
> to restore from backup if there is such a crash.
>
> full_page_writes = on is required for protection of database
> integrity in most environments.
>
> In the mission critical environments I've worked with, it has
> generally been desirable to preserve database integrity and to be
> able to recover from an OS crash faster than can be done from
> backup.
>
> --
> Kevin Grittner
> EDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>