Re: Linux on CF-Cards
On Tue, Jan 20, 2004 at 04:53:15PM +0100, Urs Nietlispach wrote:
> I'm on this list since a few weeks - but actually I'm not really sure if I'm right here.
> What I'm looking for is not so much 'embedded' in terms of very little space like 8MB (the 1 lb bag..),
> what I'm looking for is a linux which can be run stable for years on a CF card. The main goal is stability, but there should also be SSL and the standard network featurs. A GUI is not needed.
> Can anybody tell me where I can gather information about this?
> What are the main approaches to keep the CF card alive?
A lot of applications do not need write access,
or if they do(logs,..), writing to a RAM based fs(tmpfs,ramfs) works
for things not requiring permanent storage.
So easiest solution is to run on a read-only partition.
If you wish to make changes, remount as rw, make changes, then go
back to ro.
Or use a few partitions, the main one ro, and a data partition mounted rw.
You can compress about 2 to 1 with cramfs, but it's read only.
jffs2 is designed for flash, and offers both write and compression,
but I don't know if it makes sense to use it on CF.
The longevity/reliability of flash for write operations is an interesting
area to research. The vendors don't tell you a whole lot, or if they
do it is not very specific. SanDisk has got some whitesheets on their
site about wear leveling built in.
http://www.openbrick.org project has a wiki with some good notes on CF.
Sandisk is selling a Industrial grade that is rated at 2M read/writes
instead of 300K.
I was very interested in the wear leveling built in. From what SanDisk
white paper tells, their controller wear-levels over smaller block areas,
not the entire flash disk area. They suggest that some filesystems
will move a file around enough on re-write to spread out the wear.
I would like to find time to study file-system behavior to track
where exactly on the disk it is writing files too. Anyone know
how to determine what is the physical placement on disk of a certain
I was looking for some inexpensive IDE to CF converters on ebay,
ended up buying some IDE with CF modules attached:
I'm guessing that it's something thrown together by a hobbyist,
but the price is right, and you have to like the domain name :)
Haven't got em yet, so I can't comment further.
So that has me wondering if the cheap USB flash stick I bought
does wear leveling...