CD-ROM changers

CD-ROM changers

Post by jg.. » Wed, 08 Mar 1995 16:32:09



Hi,

I would like to setup a BBS under LINUX and was wondering if I can use
a Pioneer 6-disc changer?  If so, what would happen if more than one
user attempted to download something?  Is there a way (without programming
modifications) to have it copy the file to the hard drive thereby freeing
the CD-ROM changer for other users?

Thank you!


 
 
 

CD-ROM changers

Post by Joe Bu » Thu, 09 Mar 1995 02:52:06



>I would like to setup a BBS under LINUX and was wondering if I can use
>a Pioneer 6-disc changer?  If so, what would happen if more than one
>user attempted to download something?  Is there a way (without programming
>modifications) to have it copy the file to the hard drive thereby freeing
>the CD-ROM changer for other users?

In theory, one could write a device driver that would make your disk
changer look like six different normal disks, so that any program that
accessed them would work normally (though slowly) without any code
changes.  Linux caches recently accessed disk files in memory where it
can, so that if you had lots of RAM things might not be so bad for file
access.

There is one serious problem: Linux does not have a notion of a disk
drive that is slower than the swap area, so when an executable is
paged out, the text section (the code) is read back in from the original
executable rather than from the swap area.  This is slow on a regular
CD-ROM; it would be really slow with your disk changer pointing to
different disks.  Ideally Linux would be able to page the whole executable
to the swap area when a slow device is being used (in general this would
mean you'd need a bigger swap area).

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