Flash File System Concerns

[Daris A Nevil]

Prakash,

You don't have to worry about the /proc filesystem, as it is indepedent of
your Disk or Flash filesystem.

I usually point the /var/log directory to a RAMDISK.

Regards,
Daris
SNMC

Prakash kanthi said:
>
> Folks,
>
> I have one concern regarding FFS. If you use flash for
> your entire filesystem including /var/log, /proc,
> etc.., you will be accessing flash too many times.
>
> And there is good chance that, your flash on the board
> reaches maximum number of accesses/writes limited by
> flash technology.
>
> How do people generally handle that in the industry.
> Especially, if you have on-board (non-replaceable)
> flash?
>
> Thanks,
> Prakash
>
>
> Jaap Jan: Thank you very much for precise
> instructions.
>
>
>
>
> --- Jaap-Jan Boor <jjboor at lucent.com> wrote:
>> Prakash,
>>
>> You should divide your flash into parts. e.g.:
>>
>> - first block(s) boot
>> - then some blocks for the kernel
>> - all remaining blocks as root fs
>>
>> You do this partitioning in the maps directory of
>> drivers/mtd.
>>
>> You can make a linux kernel with mtd and jffs2
>> support and ramdisk that
>> holds the erase, eraseall, dd, mkfs.jffs2 etc.
>> programs.
>>
>> You can load the kernel into SDRAM, run it, prepare
>> your flash (erase flash, then use mkfs.jffs2 on a
>> /dev/mtd? device
>> to prepare an fs.
>>
>> You should then make a new kernel that uses mtd as
>> rootfs, not
>> the ramdisk as rootfs.
>>
>> Jaap-Jan
>>
>> Prakash kanthi wrote:
>> >
>> > Hi Jaap Jan,
>> >
>> > Thanks for your reply. What do you mean by 'works
>> out
>> > of the box with denx'? I see the code you referred
>> to
>> > but not sure how to use it. I still have some
>> > concerns. Like,
>> >
>> > 1. How can i initially store the image into flash?
>> My
>> > flash chip is on the board.
>> > 2. How can i boot linux from flash?
>> >
>> > 3. Currently i have a 32MB SDRAM along with flash.
>> I
>> > have tools to download linux image into SDRAM.
>> Even if
>> > i go with MTD/JFFS, my concern is unless linux
>> runs
>> > flash can not be accessed and vice versa.
>> >
>> > 4. Lets say, i download linux into a safe place in
>> > SDRAM, boot it and then access flash thru MTD/JFFS
>> and
>> > store linux image into flash. Even in this case,
>> what
>> > all i need to take care of for making my flash a
>> boot
>> > device.
>> >
>> > Any detailed documentation is appreciated.
>> >
>> > Thanks,
>> > Prakash
>> >
>> > --- Jaap-Jan Boor <jjboor at lucent.com> wrote:
>> > > Hi,
>> > >
>> > > I use strata flash with MTD and JFSS2 as file
>> system
>> > > on top of it. Works out of the box with denx'
>> eldk
>> > > kernel and
>> > > toolchain. I've provided my own flash map but
>> you
>> > > can also use an existing one (look e.g. in
>> > > linux/drivers/mtd/maps)
>> > >
>> > > Jaap-Jan
>> > >
>> > > Wolfgang Denk wrote:
>> > > >
>> > > > In message
>> > >
>> <20030326070131.88176.qmail at web41202.mail.yahoo.com>
>> > > you wrote:
>> > > > >
>> > > > > I have a 32MB Intel Strata flash on my
>> PPC405
>> > > based
>> > > > > custom board. I need to create access
>> > > routines/APIs to
>> > > > > access the flash. I was thinking of creating
>> a
>> > > Flash
>> > > > > File System and mount it as a device in
>> Linux
>> > > > > environment.
>> > > > >
>> > > > > Are there any off the shelf FFS packages
>> > > available?
>> > > > > Generally, how the flash is used?
>> > > >
>> > > > Use the MTD layer.
>> > > >
>> > > > > I am working with micro-monitor to use its
>> Tiny
>> > > File
>> > > > > System on flash support and eventually mount
>> > > into
>> > > > > linux. Did anyone use this combination
>> before?
>> > > >
>> > > > I think you cannot do this. AFAIK the TFS code
>> is
>> > > not available under
>> > > > a GPL compatible license which prevents it
>> from
>> > > being linked with the
>> > > > Linux kernel code.
>> > > >
>> > > > Best regards,
>> > > >
>> > > > Wolfgang Denk
>> > > >
>> > > > --
>> > > > Software Engineering:  Embedded and Realtime
>> > > Systems,  Embedded Linux
>> > > > Phone: (+49)-8142-4596-87  Fax:
>> (+49)-8142-4596-88
>> > >  Email: wd at denx.de
>> > > > There is is no reason for any individual to
>> have a
>> > > computer in  their
>> > > > home.      -- Ken Olsen (President of Digital
>> > > Equipment Corporation),
>> > > >               Convention of the World Future
>> > > Society, in Boston, 1977
>> > > >
>> > >
>> > > --
>> > > J.G.J. Boor
>> > > Room:  BE-525
>> > > Lucent Technologies Nederland b.v.
>> > > Phone: +31 35 687 4721
>> > > Optical Networking Group TMS Data
>> > > Fax:   +31 35 687 5976
>> > > P.O. Box 1168, 1200 BD, Hilversum, The
>> Netherlands
>> > mailto:jjboor at lucent.com
>> >
>>
>> --
>> J.G.J. Boor
>> Room:  BE-525
>> Lucent Technologies Nederland b.v.
>> Phone: +31 35 687 4721
>> Optical Networking Group TMS Data
>> Fax:   +31 35 687 5976
>> P.O. Box 1168, 1200 BD, Hilversum, The Netherlands
> mailto:jjboor at lucent.com
>
>


Daris A Nevil
Simple Network Magic Corporation
401 Kentucky
McKinney, Texas 75069
http://www.snmc.com
972-562-3751


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