Read-Only RAID-5 on DVD? :-)

[ubuntu at rio.vg]

Harijs Buss wrote:
> Hello!
> 
> The lifetime of DVD+-R disks is probably even shorter than that of CD-R. 
> 
> Thinking about backups written on DVD+-R, should be logical to use the same 
> technology as RAID-5: for example, write 4 DVD disks containing as much 
> information as usually 3, but with redundant information which would allow to 
> restore all info even if one (any) of these DVD's become unreadable or has 
> been lost. 
> 
> For privacy lovers, these 4 (or more) DVD's could be stored each at different 
> location; only when somebody has been able to collect at least 3 of them he 
> would have the information available :-)  Certainly, 4 was mentioned only as 
> example, this might be any number starting from 3 or more (like hard disks in 
> RAID-5). 
> 
> As it happens with all good ideas, probably somebody has already thought about 
> that and made some software to burn such read-only DVD RAID-5  :-)  Please 
> help me with link to existing software. 
> 

I'm reasonably certain that isn't possible.  The filesystem used on CDs
and DVDs doesn't support raiding, as far as I'm aware.  Moreover, you'd
need a single machine with at least 3 DVD-ROM drives to read the disks,
which rather cuts down on their usefulness.

If you REALLY wanted to do it, I suppose you could just do it with
images.  Create four loopfs files, place a raid fs on them, copy the
data you want, then umount them and copy each loopfs file to DVD...