On 1/23/17 6:14 PM, Peter Geoghegan wrote:
In practice, Postgres checksums do *not* seem to
catch problems. That's been my experience, at least.

For someone running on a bunch of AWS hardware that doesn't really surprise me. Presumably, anyone operating at that scale would be quickly overwhelmed if odd hardware errors were even remotely common. (Note that odd errors aren't the same as an outright failure.)

Where I'd expect this to help is with anyone running a moderate-sized data center that doesn't have the kind of monitoring resources a cloud provider does.

As for collecting data, I don't really know what more data we can get. We get data corruption reports on a fairly regular basis. I think it's a very safe bet that CRCs would identify somewhere between 20% and 80%. Maybe that number could be better refined, but that's still going to be guesswork.

As others have mentioned, right now practically no one enables this, so we've got zero data on how useful it might actually be. If the patch to make this a GUC goes through then at least we could tell people that have experienced corruption to enable this. That might provide some data, though the horse is already well out of the barn by then.
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532)

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