UBIFS data integrity

[rcrb rcrb]

On Tue, Jan 14, 2014 at 10:32 AM, Mats Kärrman <Mats.Karrman at tritech.se> wrote:
> Hi,
>
> On Tuesday, January 14, 2014 3:51 AM, rcrb rcrb [rcrbsw at gmail.com] wrote:
>> I am considering using a database over UBIFS on my embedded device.
>> The database file is approximately 1 MiB. I wonder if I can rely on
>> the filesystem to be sure than this file will never have a corruption,
>> even in case of power cut during update. Will the filesystem guarantee
>> that, after reboot, the file will be either in the pre-update state or
>> be correctly updated ?
>
> First of all, UBIFS relies on the underlying MTD driver also
> doing its job so you should also make sure this works on your
> board.
> If your MTD driver works, UBIFS is supposed to guarantee
> that every write operation is atomic, i.e. it is either fully written or
> discarded.
> If your database is guaranteed  correct after a power-cut then
> depends on if it is consistent after every write or if it requires
> several write operations to produce a new consistent state.
> In general this requires that your database also is implemented
> in a fault tolerant way.
>
> BR // Mats

Thank you for you answer Mats. I checked the write system calls with
the database I plan to use, it appears that the transactions are
validated with only one write. So I think it will be OK.

rc