Separate startup and data partitions in Lion

It's easy to do. But unless your boot volume is small or you have a second physical drive to use for your user data, or you run applications which create huge scratch files; there's little point to it. Just use one partition and allow HFS+ to take care of business for you in the background. This is especially true with Lion due to the hidden Recovery HD partition it creates during installation as there's not even any need for a second user-created troubleshooting partition.

If you have a relatively small SSD being used as the boot volume and too much data to comfortably fit in that volume, but a relatively large second platter drive, there can be good benefits in relocating your user folder to such a larger second drive. There are no significant benefits for the average user with only one hardware device, regardless of the partitioning scheme.

Here are instructions for doing so in case you're interested:

http://m.lifehacker.com/5254923/how-to-move-your-home-folder-to-another-drive

I seperate my Data from my system and I really find it beneficial specially when doing major upgrades i.e SL to Lion for instance. I know my data is safe and, if I have to revert back to snow leopard for any reason I just have to change over the O/S drive to suit my needs. I'm running Lion now and have no problems haveing data on seperate drive. Caused no problems when upgrading neither. I didn't have to do anything different and the upgrade was without incident. everything working fine including my bootcamp windows drive. I can't remember what I did to achieve this st up but I got the help from this forum so it's available if you do a search.

Hope this helps

Denisimo

Setting up separate partitions on a single drive is a bit different than using a separate drive. There are a number of advantages to keeping certain data on a separate drive. However, there really isn't much benefit in creating multiple partitions on a single drive. You can simply create folders to do the same thing that you would use a separate partition for. Invariably, at some point, you'll find that you are running out of space in one of the partitions that you had created and you'll need to resize them. Depending on how the drive was partitioned and where the OS is stored, resizing a partition can be easy or problematic. By leaving it as one partition, you pretty much eliminate any of these problems.