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Date:   Tue, 18 Jul 2023 07:30:17 +0200
From:   Kai Tomerius <kai@tomerius.de>
To:     "Alan C. Assis" <acassis@gmail.com>
Cc:     linux-embedded@vger.kernel.org
Subject: Re: File system robustness
Message-ID: <20230718053017.GB6042@tomerius.de>
References: <20230717075035.GA9549@tomerius.de>
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Hi Alan,

thx a lot.

I should have mentioned that I'll have a large NAND flash, so ext4
might still be the file system of choice. The other ones you mentioned
are interesting to consider, but seem to be more fitting for a smaller
NOR flash.

Regards
Kai


On Mon, Jul 17, 2023 at 10:50:50AM -0300, Alan C. Assis wrote:
> Hi Kai,
> 
> On 7/17/23, Kai Tomerius <kai@tomerius.de> wrote:
> > Hi,
> >
> > let's suppose an embedded system with a read-only squashfs root file
> > system, and a writable ext4 data partition with data=journal.
> > Furthermore, the data partition shall be protected with dm-integrity.
> >
> > Normally, I'd umount the data partition while shutting down the
> > system. There might be cases though where power is cut. In such a
> > case, there'll be ext4 recoveries, which is ok.
> >
> > How robust would such a setup be? Are there chances that the ext4
> > requires a fsck? What might happen if fsck is not run, ever? Is there
> > a chance that the data partition can't be mounted at all? How often
> > might that happen?
> >
> 
> Please take a look at this document:
> 
> https://elinux.org/images/0/02/Filesystem_Considerations_for_Embedded_Devices.pdf
> 
> In general EXT4 is fine, but it has some limitation, more info here:
> https://opensource.com/article/18/4/ext4-filesystem
> 
> I think Linux users suffer from the same problem we have with NuttX (a
> Linux-like RTOS): which FS to use?
> 
> So for deep embedded systems running NuttX I follow this logic:
> 
> I need better performance and wear leveling, but I don't need to worry
> about power loss: I choose SmartFS
> 
> I need good performance, wear leveling and some power loss protection: SPIFFS
> 
> I need good performance, wear leveling and good protection for
> frequent power loss: LittleFS
> 
> In a NuttShell: There is no FS that 100% meets all user needs, select
> the FS that meets your core needs and do lots of field testing to
> confirm it works as expected.
> 
> BR,
> 
> Alan