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

[Wisely Koh]

I am positive someone did raid with diskette drives, saw it on digg
some time ago...



On 7/3/06, ubuntu at rio.vg <ubuntu at rio.vg> wrote:
> Harijs Buss wrote:
> > On Monday 03 July 2006 02:25, ubuntu at rio.vg rakstija:
> >
> >> 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.
> >
> > Nope, files might be assembled reading sequentially each DVD, just like p2p
> > programs are assembling files as different fragments arrive.
> >
>
> You'd need to write a special RAID design specifically for it.  Swarming
> P2P apps require a special file with the control information and md5sum.
>  A normal Raid5 has the filesystem written across the raid, so without
> immediate access to n-1 disks, you don't know what sectors to find the
> file to reconstruct.  So you'd have to write an entirely new raid5
> system that also kept file information on all disks.
>
> It'd require a massive amount of work to do at the filesystem level for
> benefits that are miniscule.
>
> Blank DVDs are cheap.  Why not just make two copies?
>
> It'd be possible to write a more user-level app to simulate it.  Like
> the P2P apps you mentioned, they could split a file into three or four
> parts, and keep the control info right in the file.
>
> I've never heard of such a program, the call for that sort of thing
> isn't very high.  Half the point of raid5 is the read speed benefits,
> which this system would completely lack, of course.  You'd also lose
> quite a bit of convenience...
>
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