Re: Redesigning checkpoint_segments

On Wed, Jun 5, 2013 at 11:05 PM, Joshua D. Drake <jd(at)commandprompt(dot)com> wrote:
>
> On 6/5/2013 10:54 PM, Peter Geoghegan wrote:
>>
>> On Wed, Jun 5, 2013 at 10:27 PM, Joshua D. Drake <jd(at)commandprompt(dot)com>
>> wrote:
>>>
>>> I just wonder if we are looking in the right place (outside of some
>>> obvious
>>> badness like the PANIC running out of disk space).
>>
>> So you don't think we should PANIC on running out of disk space? If
>> you don't think we should do that, and you don't think that WAL
>> writing should be throttled, what's the alternative?
>
>
> As I mentioned in my previous email:
>
>
> Instead of "running out of disk space PANIC" we should just write to an
> emergency location within PGDATA and log very loudly that the SA isn't
> paying attention. Perhaps if that area starts to get to an unhappy place we
> immediately bounce into read-only mode and log even more loudly that the SA
> should be fired. I would think read-only mode is safer and more polite than
> an PANIC crash.
>
> I do not think we should worry about filling up the hard disk except to
> protect against data loss in the event. It is not user unfriendly to assume
> that a user will pay attention to disk space. Really?

Okay, then I will say it's user unfriendly, especially for a transient
use of space, and particularly if there's no knob for said SA to
attenuate what's going on. You appear to assume the SA can lean on
the application to knock off whatever is going on or provision more
disk in time, or that disk is reliable enough to meet one's goals. In
my case, none of these precepts are true or desirable.