I already tried USB memory sticks, but they're slow (I need quick bootup times) and have limited write cycles, which is a problem for log files & swap. Due to the nature of what I need todo, I can't rely on having a hard drive for swap or log files.

The CF card works ok'ish, but it's external - I need something that's internal. where a client can mess around with th CF card. Many printers use CF to store their firmware on, and if you know you're way around it, then you'll quickly be able to bypass the authentication for print mailboxes and the company won't be able to track your print usage - this is just an example though.


In this case I'm building a NAS, that needs fast bootup times and should be fail safe. Since DOM's / CF cards / etc don't have moving parts, they don't generate (as much) heat, nor will they fail as quick as hard drives do.
B

Disk On Modules generally run on IDE busses, so they won't interfere with the SATA / SAS buses if something goes wrong on the SATA / SAS bus. SATA systems will re-map bus 1-> 0, 2->1, 3->2, etc when bus0 fails.

But, I could probably use an SSD, and run it on an individual SATA port using a SATA PCIE card, and configure it to run in IDE mode. The only problem is that I'll then have to sacrifice a PCIE bus, and slot in the PC chassis, which could have been used for a hardware RAID card or extra 10GB / Fibre NIC.