Re: Checksums by default?

On 21/01/17 17:31, Stephen Frost wrote:
> Petr,
>
> * Petr Jelinek (petr(dot)jelinek(at)2ndquadrant(dot)com) wrote:
>> On 21/01/17 16:40, Stephen Frost wrote:
>>> * Petr Jelinek (petr(dot)jelinek(at)2ndquadrant(dot)com) wrote:
>>>> On 21/01/17 11:39, Magnus Hagander wrote:
>>>>> Is it time to enable checksums by default, and give initdb a switch to
>>>>> turn it off instead?
>>>>
>>>> I'd like to see benchmark first, both in terms of CPU and in terms of
>>>> produced WAL (=network traffic) given that it turns on logging of hint bits.
>>>
>>> Benchmarking was done previously, but I don't think it's really all that
>>> relevant, we should be checksum'ing by default because we care about the
>>> data and it's hard to get checksums enabled on a running system.
>>
>> I do think that performance implications are very relevant. And I
>> haven't seen any serious benchmark that would incorporate all current
>> differences between using and not using checksums.
>
> This is just changing the *default*, not requiring checksums to always
> be enabled. We do not hold the same standards for our defaults as we do
> for always-enabled code, for clear reasons- not every situation is the
> same and that's why we have defaults that people can change.

I can buy that. If it's possible to turn checksums off without
recreating data directory then I think it would be okay to have default on.

>> The change of wal_level was supported by benchmark, I think it's
>> reasonable to ask for this to be as well.
>
> No, it wasn't, it was that people felt the cases where changing
> wal_level would seriously hurt performance didn't out-weigh the value of
> making the change to the default.
>

Really?

https://www.postgresql.org/message-id/d34ce5b5-131f-66ce-f7c5-eb406dbe026f@2ndquadrant.com

https://www.postgresql.org/message-id/83b33502-1bf8-1ffb-7c73-5b61ddeb68ab@2ndquadrant.com

--
Petr Jelinek http://www.2ndQuadrant.com/
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