Re: fault tolerance...

Tom Lane wrote:
> Christopher Quinn <cq(at)htec(dot)demon(dot)co(dot)uk> writes:
>
>
> The WAL log uses per-record CRCs plus sequence numbers (both per-record
> and per-page) as a way of determining where valid information stops.
> I don't see any need for relying on a "root block" in the sense you
> describe.
>

Yes I see.
I imagine if a device were used for the log (non-file so no
EOF to denote end of log/valid-data) there is the
possibility that old record space after the last/valid
record might contain bytes which appear to form another
valid record ... if it weren't for the security of a crc.

> check, but no one seems very excited about it. The performance costs
> would be nontrivial and we have not seen all that many reports of field
> failures in which a CRC would have improved matters.
>

Access to hard data on such corruption or its theoretical
likelihood would be nice!
Have you referenced any material yourself in deciding what
measures to implement to achieve the level of data security
pgsql currently offers?

Thanks,
Chris