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@xxxxxxxxxxxxxxx> 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
