This page "Under construction" - last edit 08:30, 30 June 2008.

Booting from Compact Flash and USB stick. 

Before implementing full remote network (BOOTP) booting, I investigated the use of CF cards (and USB sticks) as the system (C:) 'drive'.

CF cards are used with an IDE to CF convertor (available on eBay) and are thus compatible with all motherboards with IDE connectors.

USB sticks can only be used with modern motherboards with built-in USB and a BIOS that supports boot from USB. This excludes most older motherboards although in some cases it is possible to find an updated BIOS on-line (I have found no way to boot from floppy disk and then transfer control to the USB device, not even when Windwos 98se is the Operating System installed on the USB device). 

Eliminating Write operations

In all cases it is necessary to set-up the operating system so that no 'write' operations are performed on the CF card or USB stick (i.e. the C: drive - all write operartions must be to a Network Share or (small) local RAM disk).

This is because the (non-volatile) memory used in CF cards and USB stocks has a limited 'write' lifetime. Although this may by 500,000 + write oprations (which is fine for photographic use or for file back-up / storage), a Microsoft Operating system is quite capable of performing hundreds of thousands of write operations every hour of every day.

The first step to eliminating write operations is to choose the 'mobile' (i.e. laptop) option during system installation. The second step is to convince the running system that you are running in 'battery' modeand that the C: drive has been 'powered down' to conserve battery life. This shoud ensue that the Operating System postpones write operations (and indeed, all 'non-esential' disk acccess) indefinatly.

The best way to ensure you have achieved the required 'non-writing' System set-up is to use a CF card (or USB stick) that can be set to 'read only' (with a mechanical switch). If you do not have one available, burn your System onto a CD (and boot from that). Where write operations are unavoidable, either set-up a small local RAM disk or write to a Network Share.

Removing the USB (C: drive) from a running Node

Once the Node is 'up and running' and the Operating System has been convinced that the C: drive has been 'powered down' (to conserve battery life), it is quite possible to actually remove the USB stick.

This allows costs to be minimised, since motherboards can be booted one at a time (and the USB stick moved from each running motherboard to the next that needs to be 'booted up') - the drawback is, of course, that if (when) a power cut occurs only the motherboard currently 'in posession' of the USB stick will be able to recover automatically.

However since this was 'only' an interin step to a Network booting system, I did not want to waste money on purchasing large numbers of 'soon to be redundant' USB sticks.