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cdrom vs usb-hdd

Hi list,

I'd like to consult with the members of the list with a small issue I'm

We use a DebianLive-based CDROM (current version is based on Etch) to
provide a testing environment for our customers: We produce a hardware
that uses the out-of-tree Zaptel/DAHDI drivers, and mainly used by the 
very configurable Asterisk. Our product has its own setup needs. This 
leaves some room for human errors and such on setup. 

The live CD is intended to provide them an environment where things
should work. Thus it should seperate the setup issues from the hardware
problems. One keyword is that things shoud Just Work[tm]. I don't want a
customer wasting time reading documentation for doing something I could
have done automatically. There's a reasonable chance that the customer
won't read the docs (or misread them).

We currently provide a CD with every product as well as an up-to-date CD
image on our site.

One thing I'm considering is using a USB image instead (or in addition
to) the CD image. I'd appreciate your opinion on this.

Pros (for USB):
* We have more and more systems without a built-in CD. The systems we
  ship are, in fact. This can be also useful in the smaller form-factor
  space (e.g. my home server now is an AliX system).

* Our product requires USB2. Hence we're guaranteed to have at least one
  such port available. If it isn't free, a decent USB2 hub is usually
  easy to come by.

* Setup instructions. PCs have had a CD (and normally just one) for a
  long time. It's usually quite easy to explain how to boot from a CD. 
  Configuring a system to boot from a USB-HDD is a different story. The
  behaviour of different BIOSes varies. 
  - Older ones don't support it (but those are really rare now). 
  - Some require you to set to boot from "USB"
  - Some: from USB-HDD (as opposed to USB-CDROM and such)
  - Some require that you set the boot device specifically for every
    device and forget it when you remove the device
* Instructions for writing the image to a device:
  The current content of the live-manual
  (http://live.debian.net/manual/html/ch03s03.html) is mostly around 
    dd if=binary.img of=${USBSTICK}

  - All too easy for someone to accidentally write over his HD. I'd hate
    to see something like that happen to one of our customers. 
    http://wiki.debian.org/DebianLive/Howto/USB has slightly safer
    instructions, but more messed up.
  - There's a still a tiny minority of people that will need to write
    the image from MS-Windows and alike.
* Performance: A USB-HDD does not use DMA. This means that reading from
  the disk requires more CPU (with kernel-level priority). I suspect our
  application may be sensitive to that. But this requires some testing.

I'd appreciate any comments on those considerations.

               Tzafrir Cohen
icq#16849755              jabber:tzafrir.cohen@xorcom.com
+972-50-7952406           mailto:tzafrir.cohen@xorcom.com
http://www.xorcom.com  iax:guest@local.xorcom.com/tzafrir

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