Having one drive letter for several volumes?

You've got several choices, assuming how many "several" is and whether you want protection against drive failures.

RAID-0 (like spanning) is a way to combine all the drives into one drive. Beware that one drive failure will cause you to lose all your data, so backup often.

RAID-10 combines drives into mirrored pairs and then stripes the drives. Two drives are called RAID-1; four or more are called RAID-10. One drive in each mirrored pair can fail without losing data.

RAID-5 combines drives into striped array with parity - similar to RAID-5 - but one drive can fail without losing data. You need a minimum of three drives for RAID-5.

Next you need to pick whether you want software RAID or hardware RAID. Software RAID is only bootable with RAID-10. You'll need a separate boot drive for RAID-10. Hardware RAID boots all RAID levels. Also, hardware RAID typically has a write-back cache that improves performance, but only use the cache if the card also has a battery backing up the memory.

That's more information than you needed, but I'd be happy to help if you have questions.

windows spanning is similar to RAID 0 if you loose a disk you loose all data.

You might want to try un-raid.
I built my own server with the software after testing it with three drives, one for parity, and two for the data. If one drive dies, unraid parity allows you to rebuild it.
Shared directories means you can put files in a /dvd folder on each drive and map a drive on your client as //tower/dvd and it will pull info from each drive into a common cached folder. Drives do not spin up when you are browsing the lists of files.

It supports up to 12 x 750 GB hard disks in a server, with storage of 8.25 TB available.

http://lime-technology.com/

Does 2003 allow you to mount drives at paths instead of just at letters? I know XP can do that... this might be simpler, particularly if your drives already have things on them...

Right, as dandirk said, spanning is like RAID-0. I don't think it's bootable with Windows, but I could be wrong.

BTW, this is the way I have my system configured - Windows spanning, that is. I have two 250GB drives that I used to store a 400MB music collection. It was a real pain in the ass to balance the files across those two drives. One was always full, forcing me to move files around. So I used spanning in WinXP Pro to combine the drives into one non-bootable 500GB drive mounted as M:. And I religiously backup M: to a 500GB USB drive that I keep offsite. It's taken me a LONG, LONG time to rip all this music, so backups are crucial.

The unRAID product mentioned above is a DIY NAS box. That's also something you should consider if you want to share the data. There are lots of cheap NAS boxes out there, such as Buffalo, LaCie, Snap, etc. FWIW, I chose to NOT go down this path because I don't like the performance of low-end NAS boxes. Nothing beats the performance of local drives. Also, I share the music on this spanned set of drives to the other machines in the house (including an Xbox-360 acting as a media extender) by simply sharing the drives and making sure this machine is always on.

Yeah, I agree with not trusting a single, big ol' backup file. I use SecondCopy - do an Internet search. Or even simpler, assuming that you don't have any system files or other "uncopiable" files, then you can simply drag-and-drop the files to the backup disks. Know what I mean?

BTW, I haven't heard the term drawer discs. Is that some sort of removable media?

Ah, like a removable ATA or SATA drive? Yeah, I know what you mean. Sorry. Those are great for backing up to and taking off-site.

Hmm. Maybe Norton Ghost? I'm pretty sure it supports copying a volume to multiple CDs or DVDs, so maybe it supports copying to multiple hard disks.

If you are using MS 2003 then consider DFS. It is one of the best things MS has incorporated into their OS and one of the least used. DFS lets you introduce a global namespace which can abstrakt all of your shares. It is straightforward to setup and free with 2003 and other server OSes.

I have 4 computers that have shares abstracted through the namespace. About 20 drives over 3TB and I represent them through 3 drive letters. I can map from anywhere in the house and easily access these resources.

There's upsides and downsides to spanning drives. If you have one drive die it's a real rats nest trying to clean up the mess. I prefer to mirror all my drives. That way I'm covered in the event one drive fails. If two drives fail, well, that's what backups are for. RAID5 is nice but it requires another drive along with it's power, heat and necessary bus connections. For an HTPC the performance hit suffered by RAID5 on writing might not be that big a deal.

Since windows 2000 you've had the option to mount a drive as a letter or as a subdirectory of another drive. But this doesn't balance the available free space. You're still stuck with the space available within that branch of the directory tree. So instead of stuff on d:\\data\\whatever and e:\\data\\whatever you'd have d:\\data\\ and d:\\data\\stuffonE

Personally I've found it's less of a hassle to just get bigger drives and mirror 'em. That and using firewire 800 is nearly as fast as onboard I/O. What I've yet to try is spanning across mirrored drives. That would alleviate the drive letter hassles without risking too much of the complete data loss on a single drive failure. But the trouble is dealing with monitoring. Once you start getting into monitoring the drive health you start talking about much more expensive drive controllers. But as always, it's a matter of "good, fast or cheap, pick two."

I played with DFS some time ago, but it sounds like I should look again.

Question: What happens if a disc fails on one of the computers? I assume the namespace remains, but the files contained on that disc are not present? Is that correct?

So, unlike spanning, there is no risk to the data on the remaining good discs?