linux-ext4 - Re: [Bug 70121] New: Increasing efficiency of full data journaling

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Date:	Wed, 05 Mar 2014 15:37:30 -0500
From:	Phillip Susi <psusi@...ntu.com>
To:	bugzilla-daemon@...zilla.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: [Bug 70121] New: Increasing efficiency of full data journaling

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On 2/6/2014 5:38 AM, bugzilla-daemon@...zilla.kernel.org wrote:
> Full data journaling provides the ability that it is guaranteed
> that a file will never be saved visible for the user in a damaged
> state (except a hardware defect appears afterwards). But this has
> the disadvantage that the writing througput is ~halfed as all files
> are written 2 times.

It does no such thing.  To do that, a new kernel api is needed to
allow the application to specify where transactions start/stop.  Data
journaling only makes sense for an external journal on an ssd or
similar: then fsync() and friends can return as soon as the data hits
the ssd and rely on it being safely migrated to the hdd in the future.


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