linux-ext4 - Re: ext4 settings in an embedded system

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Date:	Fri, 16 Nov 2012 09:56:44 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Ohlsson, Fredrik (GE Healthcare, consultant)" 
	<Fredrik.Ohlsson@...com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: ext4 settings in an embedded system

On 11/14/12 4:41 AM, Ohlsson, Fredrik (GE Healthcare, consultant) wrote:
> Hi,
> I would like to have advice regarding features and options.
> I am working with an embedded system equipped with an IDE Flash Disk
> and the ext4 filesystem. I have identified 3 problems that I would
> like to solve in our product. The power is abruptly turned off from
> time to time, this has sometimes resulted in broken Superblock
> (inode8) and empty files with size 0 bytes. It also happens that file
> changes is not committed to disk even if minutes pass before a power
> loss. This is very undesirable and expensive in our case, we are
> searching for a solution or a workaround to the problems.

> List with my problems I like to solve:
> 1. Broken Superblock (inode8).
> 2. Empty files, size 0.
> 3. Very long auto commit times, several minutes with default settings.
> 
> 
> Is ext4 a bad choice for an embedded system with I 1Gb IDE Flash Disk
> and Debian 2.6.32-5-686? Should we change filesystem?
> 
> I am planning to set the mount flags: barrier=1, commit=1 and
> data=journal, is this the way to go with an embedded system and ext4?

When you say "with barrier=1", were you using barrier=0 (or "nobarrier")
before?

If you have disabled barriers explicitly, just start with re-enabling
them.  If your software is doing all the right data integrity syscalls,
then that is probably enough.

-Eric

> Is there more ext4 options/settings I can use to get an embedded
> system reliable when a power loss occurs?
> 
> Best Regards
> 
> Fredrik Ohlsson
> Software Engineer
> 
> 
> 
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