on the second drive, even if I change the second drive. Can Linux copy itself while it is running?
Yes, but you'll have inconsistencies if files change in the middle of the copy. For the most part it's not a big issue though.
I would boot the FC4 CD/DVD in rescue mode and use dd to make an image backup:
dd if=/dev/hda of=/dev/hdc bs=65536
make sure you get your drive device identifiers right or you'll hose your disk without warning. This also assumes the 2nd drive is at least as big as the first drive.
I may even use software RAID mirroring - though that would prevent me from switching to different drives with different data in the second drive slot (or can it be turned on and off easily?)
No, sw RAID is not really useful for offline backups.
- SHARING DATA - users should be able to access the same /home
directory whether running on the new system or on another machine on the network which is running Suse 9.0. I'm guessing that /home would not even have to be on a separate partition, though it is probably wise to
You can share /home over the LAN using NFS, and that is quite common. See the many how-tos on setting up NFS.
do that. It would be nice if I could also share data with the Windows machine. I'm not sure if, for example, the Mozilla prefs/user files are the same for Windows as Linux, so that I could access my email from Windows or from Linux and not have the mail end up in different places.
Almost definitely not possible for numerous reasons.
- SHARING APPS - I currently have Mandrake 8.1 installed on the
machine that I am targeting for Fedora. It would be great if I could run some of the apps already installed with Mandrake, while I am running
Hmm, may be possible, though shared library conflicts might be an issue. Almost definitely not worth the hassle though as it will royally screw up RPM in both FC and Mandrake if you share /usr.
- MIGRATING TO OTHER HARDWARE - Another bonus would be if I could take
my hard drive with Fedora installed, and pop it into my Pentium 4 (usually running Windows) to run an app that needs more juice. I could
Hard to do because of the mkinitrd boot image which will contain IDE drivers to boot on your P3 but not your P4. You could probably fudge it to boot on both but this would be VERY advanced. Plus, kudzu would go mental each time the hardware changed. Again, not worth the hassle.