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Re: Debian router (compressed FS needs)

>> Some might question themselves about "How many writes can I do to a
>> flash
>> disk?", well it depends on the manufacturer, some have internal wear
>> levelling mechanism like sandisk (there's a sandisk paper about this but
>> I
>> haven't the link here now). There is a nice discussion about this in
>> some
> Another big problem is: _when_  does  the  device  perform  the  wear
> levelling? For example, many (most ?) CompactFlash cards do this only
> at  power-on,  so  if  your system does not get rebooted on a regular
> base you better don't relay on any wear levelling on such devices.

I can only speak about the sandisk paper I read. According to what they
say, the disk is divided into "zones". Each zone has typically 4MB. In
each zone there are a few "spare" blocks, which they call "erase blocks"
(IIRC). Every time a write is performed to a specific block, physically it
is written to a different block inside the zone it belongs (to one of the
erase blocks). So even if the address to where you write is the same,
physically you are writing to a different block every time. At least this
is what they claim in their paper.

> Well, maybe I should also point out that there are  ways  to  make  a
> read-only filesystem look as if it was writable; this is very usefult
> first  to  find  out  which files are actually writeen, and second to
> redirect these writes to a (small) writable device or partition.  For
> more  information about the "mini_fo" Overlay Filesystem for Embedded
> Systems see  http://www.denx.de,  ftp://ftp.denx.de/pub/mini_fo/  and
> especially http://www.denx.de/PDF/Diplomarbeit-MK-1.0-net.pdf

Thanks, I'll take a look at that.

I forgot to say one thing... I mount the ext2 partition with the option

To see which files are written I simply use find.

Bruno Gravato.

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