Re: Debian router (compressed FS needs)
>> Some might question themselves about "How many writes can I do to a
>> disk?", well it depends on the manufacturer, some have internal wear
>> levelling mechanism like sandisk (there's a sandisk paper about this but
>> haven't the link here now). There is a nice discussion about this in
> 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.