How Many CDs Can You Burn at Once?

kfs27 asks: "In an attempt to help a professor of mine record and duplicate his lectures. I have been asked to put together a CD duplicating box. Commercial products seem to be very expensive and I figured a PC with some SCSI160 Cards (HW or SW Raid maybe), SCSI Burners and a 15K RPM drive (size not an issue) could do the job for cheaper. But the question is, how many CDs can you burn at once of 30 minutes, mono audio. 10 at a time would be excellent I think. More of course better. Cost is not a huge issue, as long as it's less than Commercial Duplicators, it's more of an experiment, but must be stable and easy to operate (I'd be willing to script up a frontend)."

Comments

Plextor Replex Tower

[haplo21112]

The Plextor Replex tower would be a much better way to go...it and its software are made for this sort of thing and are reasonablely cheap...about the same cost as what you are suggesting, after a quick calculation in my head..

don't use a RAM disk

[MSG]

First, I have to say that I agree with the comments already posted suggesting that you just compress the audio and make it available for download. It's much more efficient. Especially when semester end comes and students want to review data from several lectures, not swapping disks frequently will be more convenient.

I'd mod them up if I didn't have to say that RAM disks are a bad idea. If you simply add the RAM to the system, then the OS can cache the data in the most efficient manner possible. As long as you have the RAM to cache the image, the OS shouldn't be reading it from the drive constantly. Using a RAM disk is actually harmful to system performance, because the OS may not be able to cache disk sectors that are frequently needed. Statically allocating the RAM only works if you have more information about disk use than your OS, which you almost certainly do not.

Re:Umm, depends.

[polymath69]

The AC is right; it wouldn't make sense to mount the ISO itself, as it's the image that's of use to the burner.

But here's an even better idea. Skip the ramdisk. Instead, create a bunch of named pipes like np1..np10. Then start up a bunch of cdrecord instances, each reading from one of the named pipes. They should all block until they fill their input buffers.

Next, use tee to copy the ISO image from the hard disk into each of the pipes.

$ tee np1 np2 np3 np4 np5 np6 np7 np8 np9 < file.iso > np10

That reads the ISO from the disk only once, and so should have the same performance advantages as setting it up in a tremendously large RAM disk (the contents of which might get swapped out anyway.)

Note that the final named pipe was redirected to, rather than named as an argument to tee. That avoids the need to write an extra copy out to /dev/null.

Will it work? You'd have to try it...

Do the math!

[Rick the Red]

He doesn't want to do this once, he wants to do it many times a year, for each of the professor's lectures. If he had "orders over 500" then buying in bulk would make sense; but if he only needs 30-50 copies of each lecture (my guess) then he doesn't want to make them one at a time (but ten at at time would be OK) and he doesn't want/need to buy 500 from a service. If he's making 30 copies of 20 lectures that's 600 CDs, not 50, so it's more like $4/CD if the equipment costs him $2000. But your way would cost $0.89x500=$445/batch (not the $125 you claimed -- your math is flawed somewhere) x 20 batches = $8900 (plus throwing away 9000+ unneeded CDs). Clearly the $2000 homemade box is cheaper for this application, and if he needs more than 30 copies of each lecture it's even cheaper.

Of course, another way around this would be to put CD burners on 10 existing PCs in a lab somewhere. Not as convenient, but workable and cheaper (assuming they can get time to use that lab :-)

Re:Do the math!

[joshsisk]

You said:

your way would cost $0.89x500=$445/batch (not the $125 you claimed -- your math is flawed somewhere)

I said:

If he's building a system for $2000+ to make 50 cds when he could just pay $125 bucks instead, he's crazy.

I think your reading is flawed somewhere, I specifically wrote FIFTY, not 500. (The 500 number, which you took from elsewhere in my comment, was an example of the pricing curve of CD-R services. Note the first paragraph where I say you can get 30-50 made for $2.50 each.)

Again, it still seems cheaper to just get the CDs made as you need them. You pay $125 for each batch (assumming a batch of 50), never have to worry about bad burns, don't have to have someone spend their time "scripting a frontend" or any of that business. Also, you never have to worry about your hardware going bad, or anything really.

. If he's making 30 copies of 20 lectures that's 600 CDs, not 50, so it's more like $4/CD if the equipment costs him $2000.

And furnacecd (and others, I assume) will make cd-r batches as small as ONE cd-r for $2.50 each, with the price dropping the more you make. If your way gets the price down to $4 a CD, it's still cheaper to use a service- $2.50 each at the most. Of course, over several years, using your own equipment will become cheaper- but that's not including time for maintenence, replacing hardware if it becomes needed, setup and actually doing the work.

It also means an investment of hardware and capitol for something they might decide wasn't the best way of distributing the lectures in the first place. If, after one $125 outlay through a service, they realized that the students didn't even use the CDs, they could just not make another batch. No $2000 and all the time wasted.

I'd recommend getting the first batch made through a service for this reason even if they plan to build the equipment. That way they can see if the students even want this. I can easily see the professor asking for a show of hands "who listened to my lectures on the cd?" and only one or two students raising their hand.

Another thing to consider is the space taken for this equipment, and the hassle of requisitioning the hardware. I have worked in the University environment, and in my experience you can do small funding outlays (under $500) with little or no problem... But have to do proposals and seek bids for more expensive items.

Incidentally, I agree with others on here that the best way to distribute lectures is via the web- why even bother making CDs in the first place? Just let them download them, or listen in the library/their home pc.

Disk Changer

[Anonymous Coward]

If the creation of the disks isn't time sensative, you might want to consider some sort of CDRW coupled to a disk changer, so that you don't have to sit there the entire time waiting for it to spit out disks. At 6x write speed 30 minutes of audio is written in 5 minutes, so that would be about 4 hours for fifty copies. Not too bad if you don't have to sit there feeding the drives.