[lug] writeable CD curiosity

D. Stimits stimits at comcast.net
Wed Feb 11 16:39:58 MST 2004

David Anselmi wrote:

> D. Stimits wrote:
> [...]
> > Another possibility that I wonder about only for curiosity, and not
> > necessarily for logging, is the concept of a RAID 1 where the
> > partitions being mirrored are (a) a ram-based filesystem and (b) a
> > rewriteable CD system...if power fails and ram is flushed, then the CD
> > is used for rebuilding the array; or while power runs, the CD could be
> > ejected and saved, a new CD added, and have it automatically rebuild
> > the array via copy from ram to CD-RW. What are the hardware
> > limitations to this?
> If you're going to write to the CD-RW as though it were a hard drive,
> why not use a hard drive?  What you describe seems to add nothing but
> poor performance and (relatively) short media life.
> OTOH, if you log to a ramdisk it would be easy to hook cdrecord into
> your logrotate jobs so that current logs are kept on disk and old logs
> on CD.  Then use CD-R instead of CD-RW and they won't be erasable.
> But do you really want to lose the most recent X minutes of logs when
> your machine crashes?

Nope, this is more curiosity. But the point is to have something like a 
ring buffer of logs on CD, so that the last 650 MB or so of logs are 
always preserved, and if needed, a cheap CD-RW is just ejected and a new 
one added. Ideally it would not keep writing over it again and again, 
but if something were suspicious, one could pop the logs out and put in 
a new CD without stopping to pause or reboot or umount/mount the 
/var/log/ directory. A preserved CD is far more reliable than say a box 
of 100 hard drives.

The other thing is a goal to remove all hard drives for reliability 
reasons. Writing to a RAID system of CD-RW mirrored to a ram partition 
means the ability to pop out bad media or media at any snapshot in time, 
to browse or possibly rebuild conditions at the moment of the CD-RW 
being ejected. Again, part if this is just curiosity, one of those 
things like solving crossword puzzles that is entertaining.

D. Stimits, stimits AT comcast DOT net

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