Hello list!

Hello list!

[gianluca]

Hello list!

I am working on a selfmade board with ARM9 and eMMC as storage.
The final product will be a logger (from solar-inverter, to bus-logger, 
etc.,...) so I choose a rootfilesystem with NILFS2.
The distro is a deboostrap based for ARMEL Debian Wheezy 7.2.

I changed the critical filesystem folders (/var, /var/log, /tmp...) to 
be tempfs in ram for obviously reasons and the rootfilesystem is nilfs2 
based with a noatime option activated.

The protection period is set at 60 seconds because the application can 
write data even in shorter periods, but 60 seconds it is a average value 
to have a disk-full problem away from normal-user.

What about the wear-leveling of this configuration of the eMMC device?

Can you point me on some tools, utilities to check out this issue?

Best regards,
-- 
            ,,,
           (o o)
======oOO==(_)==OOo======

Gianluca Renzi
R&D
phone: +39.0542.609120
fax:   +39.0542.609212

       .oooO  Oooo.
======(   )==(   )=======
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===================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
  \ source code!  /
   ---------------
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Re: Hello list!

[Clemens Eisserer]

Hi Gianluca,

> What about the wear-leveling of this configuration of the eMMC device?

Actually nilfs2 is by design as friendly to flash devices with a weak
controller as possible.
It only performs sequential writes, yielding a perfectly equal
distribution of writes across the device.
Nilfs2 even overwrites static data which won't be written to when
using other filesystems - which is great for devices supporting only
dynamic wear leveling (usually SD, mmc, emmc, ...).

However, there is one issue left - the (two) superblocks are written
to periodically in short intervals.
There is currently an ongoing discussion about this and Andreas has
posted an experimental patch which works well on my raspberry pi.

> Can you point me on some tools, utilities to check out this issue?

What I did to observe the write-patterns of various file-systems was
to create a ram-disk using BUSE: https://github.com/acozzette/BUSE
It delivers an example-program which can be modified to log each
write-access, which I imported as CSV into LibreOffice for
visualization.

Regards, Clemens
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Re: Hello list!

[gianluca]

On 02/12/2014 02:04 PM, Clemens Eisserer wrote:
> Hi Gianluca,
>
>> What about the wear-leveling of this configuration of the eMMC device?
>
> Actually nilfs2 is by design as friendly to flash devices with a weak
> controller as possible.
> It only performs sequential writes, yielding a perfectly equal
> distribution of writes across the device.
> Nilfs2 even overwrites static data which won't be written to when
> using other filesystems - which is great for devices supporting only
> dynamic wear leveling (usually SD, mmc, emmc, ...).
>

Ok. good news to me.

> However, there is one issue left - the (two) superblocks are written
> to periodically in short intervals.
> There is currently an ongoing discussion about this and Andreas has
> posted an experimental patch which works well on my raspberry pi.
>

What patch? Can you give some additional info? I am running kernel 
3.12.2 vanilla.

>> Can you point me on some tools, utilities to check out this issue?
>
> What I did to observe the write-patterns of various file-systems was
> to create a ram-disk using BUSE: https://github.com/acozzette/BUSE
> It delivers an example-program which can be modified to log each
> write-access, which I imported as CSV into LibreOffice for
> visualization.

can you explain better?

Regards,
-- 
            ,,,
           (o o)
======oOO==(_)==OOo======

Gianluca Renzi
R&D
phone: +39.0542.609120
fax:   +39.0542.609212

       .oooO  Oooo.
======(   )==(   )=======
        \ (    ) /
         \_)  (_/

===================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
  \ source code!  /
   ---------------
     ¯\_(".)_/¯
--
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