From: Joshua D. Drake <jd@commandprompt.com>
To: Toru SHIMOGAKI <shimogaki.toru@oss.ntt.co.jp>
Cc: Steve Atkins <steve@blighty.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: PITR Backups
Date: Fri, 22 Jun 2007 06:54:01 -0700
Message-ID: <467BD479.5090603@commandprompt.com> (raw)
In-Reply-To: <467B7A89.3080300@oss.ntt.co.jp>
References: <7E0807EE-B970-4869-A248-B838E42AD9EE@hi5.com>
<9761.1182472005@sss.pgh.pa.us>
<467B3459.9030808@oss.ntt.co.jp>
<B4AE85C4-8E1C-4EF6-B8A4-7B66C26238EA@blighty.com>
<467B7A89.3080300@oss.ntt.co.jp>
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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To: pgsql-performance@postgresql.org
Cc: jd@commandprompt.com, shimogaki.toru@oss.ntt.co.jp, steve@blighty.com
Subject: Re: PITR Backups
In-Reply-To: <467BD479.5090603@commandprompt.com>
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