"Dropsafe" logs

[Scott Crawford <Scott.Crawford () IDC CTBTO ORG>]

Greetings --

(My mail agent crashed without having logged the send when I attempted to send 
this before and it hasn't shown up on the list yet, so this *should* be the 
first time I'm posting this question, but apologies if not.)

We are seeking a means to implement real-time write-once "dropsafe" logs of our 
firewall bastion in case of a system failure or a hacker trying to cover their 
tracks.  Unfortunately, unless there's an alternative I'm not aware of, a CD-R 
requires a complete disk image in ISO 9660 format to be burned into the 
writeable disk all at once, which means we either have to wait until we have 
nearly 640 MB of logfiles to write or waste an awful lot of writeable disk 
space.  We have no operational experience with MO drives here, nor would we want 
to risk those models where write-once settings can be turned off in software. 
Sending output to a line printer is not an attractive option, nor is keeping 
around a machine that would otherwise be junk just to monitor, for example, 
serial line output from the bastion host and dump terminal sessions a few kb at 
a time to a permanent logfile.

What are others doing to maintain real-time write-once copies of firewall logs?  
Is there write-once media to which data can be written in realtime (i.e. like a 
real filesystem)?

AdTHANKSvance,
Scott Crawford