Re: PITR Backups

On Jun 21, 2007, at 7:30 PM, Toru SHIMOGAKI wrote:

>
> Tom Lane wrote:
>> Dan Gorman <dgorman@hi5.com> writes:
>>>    All of our databases are on NetApp storage and I have been
>>> looking
>>> at SnapMirror (PITR RO copy ) and FlexClone (near instant RW volume
>>> replica) for backing up our databases. The problem is because there
>>> is no write-suspend or even a 'hot backup mode' for postgres it's
>>> very plausible that the database has data in RAM that hasn't been
>>> written and will corrupt the data.
>
>> Alternatively, you can use a PITR base backup as suggested here:
>> http://www.postgresql.org/docs/8.2/static/continuous-archiving.html
>
> I think Dan's problem is important if we use PostgreSQL to a large
> size database:
>
> - 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.

What problems have you actually seen?

Cheers,
   Steve