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,=
=20
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=20
be tempfs in ram for obviously reasons and the rootfilesystem is nilfs2=
=20
based with a noatime option activated.

The protection period is set at 60 seconds because the application can=20
write data even in shorter periods, but 60 seconds it is a average valu=
e=20
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,
--=20
,,,
(o o)
=3D=3D=3D=3D=3D=3DoOO=3D=3D(_)=3D=3DOOo=3D=3D=3D=3D=3D=3D

Gianluca Renzi
R&D
phone: [phone]
fax: [phone]

.oooO Oooo.
=3D=3D=3D=3D=3D=3D( )=3D=3D( )=3D=3D=3D=3D=3D=3D=3D
\ ( ) /
\_) (_/

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
=C2=AF\_(".)_/=C2=AF
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[Clemens Eisserer]

Hi Gianluca,

Post by 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.

Post by gianluca
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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[gianluca]

Post by Clemens Eisserer
Hi Gianluca,

What about the wear-leveling of this configuration of the eMMC devic=

e?

Post by Clemens Eisserer
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.

Post by Clemens Eisserer
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=20
3.12.2 vanilla.

Post by Clemens Eisserer

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,
--=20
,,,
(o o)
=3D=3D=3D=3D=3D=3DoOO=3D=3D(_)=3D=3DOOo=3D=3D=3D=3D=3D=3D

Gianluca Renzi
R&D
phone: [phone]
fax: [phone]

.oooO Oooo.
=3D=3D=3D=3D=3D=3D( )=3D=3D( )=3D=3D=3D=3D=3D=3D=3D
\ ( ) /
\_) (_/

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
=C2=AF\_(".)_/=C2=AF
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