Re: streaming replication, "frozen snapshot backup on it" and missing relfile (postgres 9.2.3 on xfs + LVM)

From: Benedikt Grundmann <bgrundmann(at)janestreet(dot)com>
To: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
Cc: PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org>, David Powers <dpowers(at)janestreet(dot)com>
Subject: Re: streaming replication, "frozen snapshot backup on it" and missing relfile (postgres 9.2.3 on xfs + LVM)
Date: 2013-05-14 20:47:26
Message-ID: CADbMkNMN6pcrxxaiyWeZ5XFvJFX9iAn1gqwi65L_UKa5Z-0rQg@mail.gmail.com
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I think my previous message wasn't clear enough. I do *NOT* think that LVM
snapshot is the culprit.

However I cannot discount it as one of the possibilities. But I have no
evidence in either /var/log/messages or in dmesg that the LVM snapshot went
into a bad state AND we have been using this method for a long time.

The only thing that is *new* is that we took the snapshot from the
streaming replica. So again my best guess as of now is that if the
database crashes while it is in streaming standby a invalid disk state can
result during during the following startup (in rare and as of now unclear
circumstances).

You seem to be quite convinced that it must be LVM can you elaborate why?

Thanks,

Bene

On Tue, May 14, 2013 at 12:09 PM, Benedikt Grundmann <
bgrundmann(at)janestreet(dot)com> wrote:

> That's one possible explanation. It's worth noting that we haven't seen
> this before moving to streaming rep first and we have been using that
> method for a long time.
>
>
> On Tue, May 14, 2013 at 11:34 AM, Heikki Linnakangas <
> hlinnakangas(at)vmware(dot)com> wrote:
>
>> On 14.05.2013 16:48, Benedikt Grundmann wrote:
>>
>>> It's on the production database and the streaming replica. But not on
>>> the
>>> snapshot.
>>>
>>
>> So, the LVM snapshot didn't work correctly?
>>
>> - Heikki
>>
>
>

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