Re: [HACKERS] Checksums by default?

On 2/10/17 6:38 PM, Tomas Vondra wrote:
> And no, backups may not be a suitable solution - the failure happens on
> a standby, and the page (luckily) is not corrupted on the master. Which
> means that perhaps the standby got corrupted by a WAL, which would
> affect the backups too. I can't verify this, though, because the WAL got
> removed from the archive, already. But it's a possibility.

Possibly related... I've got a customer that periodically has SR replias 
stop in their tracks due to WAL checksum failure. I don't think there's 
any hardware correlation (they've seen this on multiple machines). 
Studying the code, it occurred to me that if there's any bugs in the 
handling of individual WAL record sizes or pointers during SR then you 
could get CRC failures. So far every one of these occurrences has been 
repairable by replacing the broken WAL file on the replica. I've 
requested that next time this happens they save the bad WAL.
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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