On 2/28/07, Bruce Momjian <bruce@momjian.us> wrote:
> > But if the system was shut down uncleanly as the result of a Postgres crash or
> > fast shutdown of Postgres then that isn't an issue. And many users may prefer
> > to bring the system up as soon as possible as long as they know any corrupt
> > pages will be spotted and throw errors as soon as it's seen.
>
> I don't think we should start up a system and only detect the errors
> later.
Which is, of course, how everyone else does it. On block access, the
checksum is verified (if you've turned checksum checking on). I
*really* doubt you want to pull in every page in the database at
startup time to verify the checksum or sequence. Even pages from the
last checkpoint would be a killer.
All of the databases (Oracle, SQL Server, DB2) have a way to perform a
database corruption check which does go out and verify all checksums.
If consistency is stored at the block-level, which is pretty much the
only way to avoid full page writes, you have to accept some level of
possible corruption.
--
Jonah H. Harris, Software Architect | phone: 732.331.1324
EnterpriseDB Corporation | fax: 732.331.1301
33 Wood Ave S, 3rd Floor | jharris@enterprisedb.com
Iselin, New Jersey 08830 | http://www.enterprisedb.com/
