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Re: PITR Backups

From: Toru SHIMOGAKI <shimogaki(dot)toru(at)oss(dot)ntt(dot)co(dot)jp>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Dan Gorman <dgorman(at)hi5(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: PITR Backups
Date: 2007-06-22 02:30:49
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
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:

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

Any comments?

Best regards,

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

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