Hello, A question seems to be, according to me, important : How a corruption, detected thanks to data-checksums, is fixed?
Thank you, Thomas Le 10 janv. 2018 20:39, "Andres Freund" <and...@anarazel.de> a écrit : > On 2018-01-09 20:51:17 -0500, Stephen Frost wrote: > > Greetings, > > > > * Andreas Joseph Krogh (andr...@visena.com) wrote: > > > Aha, so enabling CRC causes hint-bits to be written causing extra > WAL-logging, > > > which woudn't be the case without CRC enabled? > > > Thanks for pointing that out. > > > > Yes, having checksums enabled forces logging of hint bits. You can > > enable wal_log_hints independently too, without having checksums, to see > > what kind of an impact it'll have on your environment. > > > > A useful documentation update might be: > > > > --- > > With checksums enabled, wal_log_hints <link to the GUC's documentation> > > will be enabled and each page read or write will involve calculating the > > checksum for the page. > > --- > > > > I'd probably just replace the "Enabling checksums may incur a noticeable > > performance penalty" with the above, as it should be clear that doing > > more work implies an impact on performance and that avoids the whole > > question of trying to characterize in a general way something that can't > > be generalized (as it's workload dependent). > > -1. I think this is underplaying the cost. > > Greetings, > > Andres Freund > >
