[Fedora-livecd-list] overlay exhaustion solution ???

[John.Florian at dart.biz]

bruno at wolff.to wrote on 02/13/2014 11:34:56:

> On Thu, Feb 13, 2014 at 09:38:53 -0500,
>    John.Florian at dart.biz wrote:
> >I just had interesting (or incredibly stupid) idea concerning the 
critical
> >limitation of the live overlays where the host crashes with bus errors
> >when the temporary space for the COW is exhausted.  Is it possible to 
use
> >trim/discard support to mitigate some of the unidirectional growth for
> >when files are deleted and/or overwritten?  Conceptually it seems like 
it
> >is a good fit, but I've not investigated the practicality.  Just 
curious
> >if this has been explored or if there are easily known reasons why this
> >wouldn't work.
> 
> I don't think this will help. You aren't going to recover space from the 

> base file system, because it never changes. As more an more packages 
> are updated you are going to use more space in the overlay area. 

I figured as much otherwise somebody would have already done this.  But my 
web searches didn't seem to reveal anything so I had to ask.
 
> Portable flash drives are getting cheaper and you might consider getting 

> one large enough for a normal install and use that instead of a live 
image. 
> Depending on how much you are installing, a 64 GB flash drive is 
probably 
> large enough.

That won't help me where I'm looking at hundreds to thousands of embedded 
nodes that have very specific use requirements for being based on a live 
image.  Using a live image makes them very resilient to 
mutation/corruption and anybody can simply reset the hardware and have a 
node back to its normal working state.  You can think of this setup 
behaving much like firmware, albeit with a Fedora image.  :-)

I just have to ensure the workloads can never cause the overlay to become 
exhausted, which is sometimes easier said than done, which is why I asked.

--
John Florian
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