It's the latter, is snapshot of the durable state of the storage
system (e.g. it will never be corrupted)
Regards,
Dan Gorman
On Jun 22, 2007, at 11:02 AM, Tom Lane wrote:
> "Simon Riggs" <simon@2ndquadrant.com> writes:
>> On Fri, 2007-06-22 at 13:12 -0400, Tom Lane wrote:
>>> If you saw a problem I'd be inclined to question whether
>>> there is some upstream component (OS or disk controller) that's
>>> reordering writes.
>
>> Given thats exactly what they do, constantly, I don't think its
>> safe to
>> say that it works since we cannot verify whether that has happened or
>> not.
>
> If he's trying to snapshot at a level of hardware that's behind a
> write-caching disk controller, I agree that that's untrustworthy.
>
> If not, ie if he's snapshotting the actual durable state of the
> storage
> system, then any problems in the snapshot indicate a problem with the
> database's ability to recover from a crash. So I don't think you
> should
> tell him to not worry.
>
> regards, tom lane