ReiserFS or ext3 on USB flash drive?

[bassix-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org]

On 1/24/06, Christopher Browne <cbbrowne-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> On 1/24/06, bassix-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org <bassix-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> >
> > That is a good point that I was interested in knowing. Will ext2 be
> > OK? Will "running" an OS from flash memory greatly reduce it's
> > lifespan due to this aforementioned limitation? Can someone illuminate
> > how flash memory counts each "access"? Does access to every sector
> > count as one access? Or, if I copy an 8MB file, does that count as one
> > access? What if I copy 100 512K files (how many "accesses" would that
> > be)?
>
> I'm not certain what the granularity is, but the point is that every
> *update* moves you towards the eventual failure of the device.
> *Access* doesn't do that; *updates* do it.
>
> Copying an 8MB file would presumably involve:
>  a) Writing 8MB of data on the filesystem;
>  b) Writing a couple KB of data of filesystem metadata;
>  c) If journalling, writing the couple KB of filesystem metadata in the journal
>
> The failure of the device will most likely take place because:
>  a) There's a section of flash being used for FS metadata that you have updated
>       over and over 150K times, wearing out the flash memory, or
>  b) You have burned through the journal 150K times, wearing out the
>      flash memory used for that section of data.
>
> Note that it probably *isn't* the 8MB that will "kill you"; that isn't
> likely to be a "hot spot" on the flash device.  "Hot spots," updated
> frequently, which are likely to either be metadata (e.g. -
> file/directory entries in frequently updated directories) or journals,
> are what will quickly reach "end of life."

Christopher,

Thanks... this helps a lot. It looks like my best solution is to
install a LIVE CD to USB flash memory (and maybe put a persistent home
directory on there too). This way (from what I understand), the entire
OS will only be READ and not rewritten (with the possible exception of
my home directory). I guess as for upgrading, I'll just download a new
version when it comes out. This sounds good anyway, as the USB flash
memory will still be way faster than CD.

(FYI, instructions for Kanotix on USB):
http://wiki.kanotix.net/CoMa.php?CoMa=usb-stickEN

Thanks again for answering my questions.

-Steve.
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