Re: silent data loss with ext4 / all current versions

Hi,

On 02/06/2016 01:16 PM, Michael Paquier wrote:
> On Sat, Feb 6, 2016 at 2:11 AM, Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>> On 02/04/2016 09:59 AM, Michael Paquier wrote:
>>>
>>> On Tue, Feb 2, 2016 at 9:59 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>>>>
>>>> On 2016-02-02 09:56:40 +0900, Michael Paquier wrote:
>>>>>
>>>>> And there is no actual risk of data loss
>>>>
>>>>
>>>> Huh?
>>>
>>>
>>> More precise: what I mean here is that should an OS crash or a
>>> power failure happen, we would fall back to recovery at next
>>> restart, so we would not actually *lose* data.
>>
>>
>> Except that we actually can't perform the recovery properly
>> because we may not have the last WAL segment (or multiple
>> segments), so we can't replay the last batch of transactions. And
>> we don't even notice that.
>
> Still the data is here... But well. I won't insist.

Huh? This thread started by an example how to cause loss of committed
transactions. That fits my definition of "data loss" quite well.

> Tomas, could you have a look at the latest patch I wrote? It would be
> good to get fresh eyes on it. We could work on a version for ~9.4
> once we have a clean approach for master/9.5.

Yep, I'll take a look - I've been out of office for the past 2 weeks,
but I've been following the discussion and I agree with the changes
discussed there (e.g. adding safe_rename and such).

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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