[CLUE-Tech] Installation on secondary HDD's

[Nate Duehr]

On Jul 26, 2004, at 9:33 PM, Richard C. Savage wrote:

> I hope this is the sort of question that elicits the "Sure, no 
> problem!" response.
>  
> So long as the restriction to install a boot partition (~100 MB or 
> less) within the first 1024 cylinders on hda is satisfied,
>  
> then the rest of a Linux installation, i.e.,  /, /usr, /home, swap, 
> etc - can be installed on hdb,hdc, hdd, etc. On any secondary hard 
> drive?
>  
> Potentially, it might even be installed on sda, sdb, etc?, where these 
> might be flash drives?

Sure, no problem!

;-)

(seriously.)

Well one possible problem.  Every cell in a flash drive has a finite 
number of reads/writes before it will fail.  Running swap and modern 
journalling filesystems from flash will cause certain portions (the 
heavily used ones) in the flash to fail before the rest of the flash 
drive.

The handhelds.org project had the jffs2 filesystem for handhelds that 
specifically worked on keeping the number of reads/writes even across 
the entire flash card.  I don't know if it's possible to build a kernel 
for a desktop machine with jffs2 and to format and mount the flash 
filesystems with that instead of one of the more traditional 
filesystems, but it might be worth looking into.  Maybe they've 
continued improving it, I don't know.  I haven't booted the iPaq to 
linux (or anything for that matter) for over a year now.  (Dang, I 
really should eBay that thing.)

It really depends on how long you expect this device to last.  Keep 
swap off of the flash filesystem for sure (run without swap if you can 
get away with it if you don't have a normal disk somewhere... heck try 
to avoid it anyway... if you're swapping, you're slooooooow) and think 
a bit about your journal settings for the filesystem if you use a 
"normal" filesystem... if you can afford some write buffering where you 
could have data lost if the power goes own, consider making the buffers 
pretty big and the commit time as slow as your application will bear.

In all honesty, probably not a big deal.  Modern flash cards are rated 
for millions of operations before failure -- but if you're building a 
commercial product, you do have to think about these things.

--
Nate Duehr, nate at natetech.com