linux-ext4 - Re: resilience against power loss

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Message-ID: <53D66ADF.14170.351043D9@vicentiu.neagoe.ni.com>
Date:	Mon, 28 Jul 2014 18:23:11 +0300
From:	"Vicentiu Neagoe" <vicentiu.neagoe@...com>
To:	linux-ext4@...r.kernel.org
Subject: Re: resilience against power loss

On 28 Jul 2014 at 10:48, Lukás Czerner wrote:

> On Tue, 22 Jul 2014, vicentiu.neagoe@...com wrote:
> 
> > Date: Tue, 22 Jul 2014 19:34:10 +0300
> > From: vicentiu.neagoe@...com
> > To: linux-ext4@...r.kernel.org
> > Subject: resilience against power loss
> > 
> > Hello,
> > 
> > I'm trying to configure ext4 to prevent data corruption in case of a 
> > power loss.
> > 
> > I test by doing a cold reset right after writing to a file.
> > I tried the nodelalloc option, but the file still becomes corrupted 
> > with trailing garbage.
> > 
> > Using ext3, I either get the old version of the file, or the new 
> > version, and there is no corruption.
> > 
> > Does nodelalloc not guarantee data integrity?
> > 
> > Are there any other options that provide complete resilience against 
> > power loss?
> 
> Well, that would be fsync. It'll make sure that your data actually reach
> disk and that the disk actually write it from the cache to platters.

I don't have control over how the applications were written, yet I 
need the system to not corrupt or lose data in case of a power loss.

I have the partition mounted with the sync option but the issue still 
reproduces.
Are there no options on ext4 to provide the same data integrity as 
data=ordered on ext3? I also tested with Btrfs and there is no data 
corruption on a power loss.

Vicentiu

> -Lukas
> 
> > 
> > thanks
> > 
> > Vicentiu
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