> > > Putting xl_prev to the end helps only for direct IO WAL sync
> > > methods, else we would need it on every page.
> >
> > [There is already an XLogRecPtr on each 8k page.]
>
> Given that hardware sector size is still 512 bytes, should
> there be a way of detecting a missing 512 byte block in the
> middle of an 8K block.
> The idea of simply writing a serial counter every 512 bytes
> seems to be a good way to handle that...
No, we have CRC for that. You are not supposed to turn it off
when you see a chance, that an 8k block is not whole.
Andreas
