Re: Block-level CRC checks

On Mon, Dec 15, 2008 at 7:24 AM, Alvaro Herrera
<alvherre(at)commandprompt(dot)com> wrote:
>> Here's an updated patch against head.
>
> Thanks.

No problemo.

>> NOTE, it appears that this (and the previous) patch PANIC with
>> "concurrent transaction log activity while database system is shutting
>> down" on shutdown if checksumming is enabled. This appears to be due
>> to FlushBuffer (lines 1821-1828) during the checkpoint-at-shutdown.
>
> Yeah, I reported this issue several times.

Hmm. Well, the easiest thing would be to add a !shutdown check for
logging the hint bits during the shutdown checkpoint :) Of course,
that would break the page for recovery, which was the whole point of
putting that in place. I'd have to look at xlog and see whether that
check can be deferred or changed. Or, did you already research this
issue?

>> Similarly, I ran a pgbench, performed a manual checkpoint, and
>> corrupted the tellers table myself using hexedit but the system didn't
>> pick up the corruption at all :(
>
> Heh :-)

:(

>> Alvaro, have you given up on the patch or are you just busy on
>> something else at the moment?
>
> I've given up until we find a good way to handle hint bits. Various
> schemes have been proposed but they all have more or less fatal flaws.

Agreed. Though, I don't want to see this patch get dropped from 8.4.

ALL, Alvaro has tried a couple different methods, does anyone have any
other ideas?

--
Jonah H. Harris, Senior DBA
myYearbook.com