On Tue, Jan 24, 2012 at 2:49 PM, Robert Treat <rob@xzilla.net> wrote:
>> And yes, I would for sure turn such functionality on if it were present.
>>
>
> That's nice to say, but most people aren't willing to take a 50%
> performance hit. Not saying what we end up with will be that bad, but
> I've seen people get upset about performance hits much lower than
> that.
When we talk about a 50% hit, are we discussing (1) checksums that are
checked on each I/O, or (2) checksums that are checked each time we
re-pin a shared buffer? The 50% hit was my estimate of (2) and has
not yet been measured, so shouldn't be used unqualified when
discussing checksums. Same thing is also true "I would use it"
comments, since we're not sure whether you're voting for (1) or (2).
As to whether people will actually use (1), I have no clue. But I do
know is that many people request that feature, including people that
run heavy duty Postgres production systems and who also know about
filesystems. Do people need (2)? It's easy enough to add as an option,
once we have (1) and there is real interest.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services