Re: Checkpoint cost, looks like it is WAL/CRC

Josh Berkus <josh@agliodbs.com> writes:
>> Uh, what exactly did you cut out?  I suggested dropping the dumping of
>> full page images, but not removing CRCs altogether ...

> Attached is the patch I used.

OK, thanks for the clarification.  So it does seem that dumping full
page images is a pretty big hit these days.  (In defense of the original
idea, I believe it was not such a hit at the time --- but as we continue
to improve performance, things that weren't originally at the top of the
profile become significant.)

It seems like we have two basic alternatives:

1. Offer a GUC to turn off full-page-image dumping, which you'd use only
if you really trust your hardware :-(

2. Think of a better defense against partial-page writes.

I like #2, or would if I could think of a better defense.  Ideas anyone?
        regards, tom lane