Re: PITR Backups

Tom Lane wrote:
> Dan Gorman <dgorman(at)hi5(dot)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.

- If we don't use hardware level snapshot operation, it takes long time to take
a large backup data, and a lot of full-page-written WAL files are made.

So, I think users need a new feature not to write out heap pages during taking a
backup.

Any comments?

Best regards,

--
Toru SHIMOGAKI<shimogaki(dot)toru(at)oss(dot)ntt(dot)co(dot)jp>
NTT Open Source Software Center