resilience against power loss

resilience against power loss

[vicentiu.neagoe]

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?

thanks

Vicentiu

Re: resilience against power loss

[Lukáš Czerner]

On Tue, 22 Jul 2014, vicentiu.neagoe@ni.com wrote:

> Date: Tue, 22 Jul 2014 19:34:10 +0300
> From: vicentiu.neagoe@ni.com
> To: linux-ext4@vger.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.

-Lukas

> 
> thanks
> 
> Vicentiu
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> 

Re: resilience against power loss

[Vicentiu Neagoe]

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

> On Tue, 22 Jul 2014, vicentiu.neagoe@ni.com wrote:
> 
> > Date: Tue, 22 Jul 2014 19:34:10 +0300
> > From: vicentiu.neagoe@ni.com
> > To: linux-ext4@vger.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
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
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