Re: Page Checksums

On Monday, December 19, 2011 03:33:22 PM Alvaro Herrera wrote:
> Excerpts from Stephen Frost's message of lun dic 19 11:18:21 -0300 2011:
> > * Aidan Van Dyk (aidan(at)highrise(dot)ca) wrote:
> > > #) Anybody investigated putting the CRC in a relation fork, but not
> > > right in the data block? If the CRC contains a timestamp, and is WAL
> > > logged before the write, at least on reading a block with a wrong
> > > checksum, if a warning is emitted, the timestamp could be looked at by
> > > whoever is reading the warning and know tht the block was written
> > > shortly before the crash $X $PERIODS ago....
> >
> > I do like the idea of putting the CRC info in a relation fork, if it can
> > be made to work decently, as we might be able to then support it on a
> > per-relation basis, and maybe even avoid the on-disk format change..
> >
> > Of course, I'm sure there's all kinds of problems with that approach,
> > but it might be worth some thinking about.
>
> I think the main objection to that idea was that if you lose a single
> page of CRCs you have hundreds of data pages which no longer have good
> CRCs.
Which I find a pretty non-argument because there is lots of SPOF data in a
cluster (WAL, control record) anyway...
If recent data starts to fail you have to restore from backup anyway.

Andres