| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| Cc: | Peter Geoghegan <pg(at)heroku(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Checksums by default? |
| Date: | 2017-01-26 00:27:07 |
| Message-ID: | CA+TgmoY53xEFW_fUtgi4JX9jT4+W10bhp31Ru9572Whr+EeVCg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jan 25, 2017 at 7:19 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Thu, Jan 26, 2017 at 9:14 AM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
>> On Wed, Jan 25, 2017 at 3:30 PM, Stephen Frost <sfrost(at)snowman(dot)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
The Enterprise PostgreSQL Company
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