Toru SHIMOGAKI wrote:
>
> Steve Atkins wrote:
>
>>> - When we take a PITR base backup with hardware level snapshot operation
>>> (not filesystem level) which a lot of storage vender provide, the
>>> backup data
>>> can be corrupted as Dan said. During recovery we can't even read it,
>>> especially if meta-data was corrupted.
>>
>> I can't see any explanation for how this could happen, other
>> than your hardware vendor is lying about snapshot ability.
>
> All of the hardware vendors I asked always said:
>
> "The hardware level snapshot has nothing to do with filesystem
> condition and of course with what data has been written from operating
> system chache to the hard disk platter. It just copies byte data on
> storage to the other volume.
Right that has been my understanding as well.
Joshua D. Drake
>
> So, if any data is written during taking snapshot, we can't assurance
> data correctness *strictly* .
>
> In Oracle, no table data is written between BEGIN BACKUP and END BACKUP,
> and it is not a problem REDO is written..."
>
> I'd like to know the correct information if the explanation has any
> mistakes, or a good way to avoid the probrem.
>
> I think there are users who want to migrate Oracle to PostgreSQL but
> can't because of the problem as above.
>
>
> Best regards,
>
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