Best use of two external hard discs

Question

I have been reading the faq and some of the answers to recent questions, so I think I have the general idea, but will explain and ask for advice, as I don't want to do something stupid.
The first external disc has been running well, however it is partitioned into 4, one of which has Time Machine which is out of space. One of the other partitions has my iphoto library, and another has the iTunes/Music library. The final partition has dvd.img files.
The new (not yet "set up") disc is plugged in, running, and now awaits my attention.
From what I've read, it looks as if my objective to let the new disc handle Time Machine and transfer ? it from the older disc, then redistribute stuff on the older disc to give everything more room will provide the best result. If you agree, what is the best way to get the job done ?
Both external discs are La Cie 500GB HiSpeed USB2
Your advice will be much appreciated
Eric

Answer 1

Let me ask you a question, first: Since both externals are the same size, the new one can't back-up both your internal HD and much, if any, of the old external. If you don't have separate backups of the other partitions on the old external, would you consider returning the new drive and exchanging it for one large enough to back-up everything?
But in answer to your main question, yes, letting TM have exclusive use of the new drive is most likely your best option. That way, you have the most important part of a good backup strategy: (at least) two copies of everything important in (at least) two different places.
To transfer your backups from the current partition to the new disk, see #18 in the Frequently Asked Questions *User Tip* at the top of this forum.
When that's done, I'd recommend excluding the old partition from TM temporarily (TM Preferences > Options). Run a backup or two to the new drive and be sure you can see and restore from them properly before deleting the old partition.
Redistributing things on the old drive may be tricky, depending on where the partitions are. If they're not backed-up somewhere, you really should do so before making any changes (just in case Murphy comes visiting).
As you probably know, Disk Utility will show a diagram of them when you select the top line for the drive in the DU sidebar and click the Partition tab.
You can delete any partition, and you can expand any partition if there's empty space below it by dragging the lower-right corner down. (You may be able to shrink one by dragging it up, but only if there's enough contiguous empty space at the bottom.)
But you cannot move the top of a partition, either up or down.
You may be able to do what you need to do by copying one partition to another (use the duplicate tab just as you did with the Time Machine partition); or copy selected things from one to another via drag and drop with the Finder.