Why split my external hard drive?

There can be any number of reasons for this. For starters, this is called partitioning. To your computer, each partition looks like a separate drive. While there generally isn't much of a reason to partition your internal drive, there are some reasons for doing so with an external drive. It really depends on what your usage is. For example, if you want to use an external drive as both a TimeMachine backup and as a place to store additional files, you would want to partition it into at least two partitions. TimeMachine will keep making backups until it either fills a drive or a partition. If you don't partition the external drive and use it for TimeMachine, the backup will eventually grow to fill the entire drive (and then begin deleting the oldest backups to make room for newer ones). However, if you create two partitions on the drive, TimeMachine will only expand to fill the one partition it is backing up to. That leaves the space on the second partition for you to use as you wish.

It sounds like you may be using the external drive just for TimeMachine. If that's the case, then there is no reason to create more than one partition.

There are some more involved situations... such as installing multiple copies of OS X (for testing or other reasons), but if that's not your intent, no need to get into that.

i partitioned my external so that i could make a bootable clone as well as time machine backups. to me it just makes sense to keep as many copies of my data that i can. i've have several previous laptops (pc's as this is my first mac) fail on me and i don't ever want to lose anything. if your external hard drive is big enough it just makes sense to partition it and keep a clone in one and then your time machine backups in the other.

No it does not need to be paritioned before anything is stored on it.

Although it is better if you do, but you can still do it afterwards.

To do that all you do is drag up the partition in the partition window from the bottom right hand corner. Then click the Plus ( + ) sign at the bottom and then give it a name and format.

You can still use the Time Machine partition to store other files. Time Machine stores its backups in a folder called Backups.backupdb. So the rest of the drive can be used for whatever you like.

I do have mine partitioned so I could also clone my boot drive to that other partition. I also have a complete copy of all the data that I have on my second physical drive in my Mac on that same TM partitoin on the external. I have no problems keeping TM backups and that other data on that one partition.

You can partition it into 2 drives and store thos older file on the second partition or leave it as one whole drive and then store those older files in a folder called something like "Old PPC Files".

It really doesn't matter. I really don't know what the Apple employee was talking about.

Could you have more then one external drive? Sure why not. Do you need more then one external drive to store all your files on including TM backups? That all depends on how may and what size those files are and what size the external drive is.

Personally I think you will be fine with the 1.5TB drive for a good long time.

You are Welcome.

Good Luck and happy computing.