Re: Proposal: Incremental Backup

On Fri, Jul 25, 2014 at 7:38 PM, Josh Berkus <josh@agliodbs.com> wrote:
> On 07/25/2014 11:49 AM, Claudio Freire wrote:
>>> I agree with much of that.  However, I'd question whether we can
>>> > really seriously expect to rely on file modification times for
>>> > critical data-integrity operations.  I wouldn't like it if somebody
>>> > ran ntpdate to fix the time while the base backup was running, and it
>>> > set the time backward, and the next differential backup consequently
>>> > omitted some blocks that had been modified during the base backup.
>> I was thinking the same. But that timestamp could be saved on the file
>> itself, or some other catalog, like a "trusted metadata" implemented
>> by pg itself, and it could be an LSN range instead of a timestamp
>> really.
>
> What about requiring checksums to be on instead, and checking the
> file-level checksums?   Hmmm, wait, do we have file-level checksums?  Or
> just page-level?

It would be very computationally expensive to have up-to-date
file-level checksums, so I highly doubt it.