Re: life of CF card

On Sat, Dec 16, 2006 at 06:53:09PM -0600, Thomas Isenbarger wrote:
> Can anyone point me to an article or give me information about the  
> life time of compact flash cards?  After all the work I am putting  
> into setting up NetBSD on my Mobilepro 790, I don't want to lose it!   
> How do folks out there deal with the prospect of cards going bad?

In general, you want to minimize writes to the card.  I do this by mounting the
root filesystem read-only.  That sort of thing is a little complicated.  I mount
certain directories as ramdisks (/var/run, I think) and disable most logging
functions.  Certain files must be handled with care; most UNIX systems expect
/etc to be writeable in order to update mtab.  It takes some trial-and-error to
get it right.

This may be overkill.  Modern CF cards should spread writes over the entire
device.  This keeps wear even, extending the lifetime of the device.

> I have a Powerbook with a PC card slot and an appropriate adapter for  
> my CF card.  Does anyone have a good solution for backing up a CF  
> card using a Mac, for instance, writing the contents of the CF card  
> to a file on my Powerbook in some way?

Hopefully, the device is accessible via /dev/wd.. or something similar.  If you
know which device fd to use, you can simply `cat /dev/wd0 | gzip > backup.gz`.
But that means that, in order to restore your backup, you really ought to
restore it to a CF card that is completely identical to the card your backup
came from.  Otherwise, you will need to figure out how to mount the card and tar
up the filesystem.  I don't know the BSDs all that well, and probably couldn't
give you advice on how to do that sort of thing.

-Forest

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