Re: [HACKERS] Checksums by default?

On Wed, Jan 25, 2017 at 7:19 PM, Michael Paquier
<michael.paquier@gmail.com> wrote:
> On Thu, Jan 26, 2017 at 9:14 AM, Peter Geoghegan <pg@heroku.com> wrote:
>> On Wed, Jan 25, 2017 at 3:30 PM, Stephen Frost <sfrost@snowman.net> wrote:
>>> As it is, there are backup solutions which *do* check the checksum when
>>> backing up PG.  This is no longer, thankfully, some hypothetical thing,
>>> but something which really exists and will hopefully keep users from
>>> losing data.
>>
>> Wouldn't that have issues with torn pages?
>
> Why? What do you foresee here? I would think such backup solutions are
> careful enough to ensure correctly the durability of pages so as they
> are not partially written.

Well, you'd have to keep a read(fd, buf, 8192) performed by the backup
tool from overlapping with a write(fd, buf, 8192) performed by the
backend.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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