Clone using something like SuperDuper (inexpensive, easy to use).
Not sure I'd have a TM Partition but that's a different story. But SuperDuper will treat the one partition like a single drive. It will clone from Drive A to Drive B, only new files so it's pretty fast.
You might want to consider using the "Store Presets with Catalog" preference so that important data is saved with the catalog and cloned.
From my brief use of a Mac, about 2.5 years, the one thing that always came up was using an external drive for both Time Machine backups and that same drive for storing other files. It is not suggested to do that. A Time Machine drive should be dedicated to just that, Time Machine.
This also goes for using any of the other backup/cloning software programs available for the Mac. It is always best to have specific dedicated drives for just backups and other drives for whatever other purpose you like.
Just Shoot Me wrote: A Time Machine drive should be dedicated to just that, Time Machine.
I totally agree. And so should IMHO, a drive that has LR catalog and all associated files and images! You can take that drive to any machine that has LR app and have access to all your images and the catalog. Since image files (and previews) can take up a lot of drive space, (like TM), best to get the biggest drive you can find and dedicate only for those files.
I agree with thedigitaldog on using SuperDuper. I have it and keep 2 EHDs connected to my iMac at all times. It clones the 2nd drive with my 1st. I import all photos onto the 1st EHD and keep a backup copy of the catalog on that same 1st EHD. Lightroom works perfectly well with the photos on the EHD; there is no need to have them on your computer drive. This eliminates the process of moving files and avoids any problems with missing files. You can find SuperDuper here.
This is how I do it:
Where are the clones?
1. I have a dedicated 2TB ext USB drive (nearing completion soon) - but does not contain my slide scans which are on an another 2TB drive.
2. I use a RAID10 6TB drive that is used once in a while to "sync" its clone, manually using WinMerge
3. I have a 2TB internal drive that has (if one wants to think) the main catalog,where I dump pictures from the cameras.
BUT for me, my main LR is the ext USB 2TB drive that shuttles between the Studio and home. It is the source for sync of others.
Methods of cloning?
1. MANUAL: I use a little app called WinMerge to manually compare and sync files. The preview folders I skip as they have too many files and it is better to simply replace the entire folder with newer one. Winmerge is quick and fast and at times, when I do a much more lengthy binary compare, has pointed out image files mismatch - and I discovered a corrupted file (half had some green issue), which I could fix from the clone that was fine. Binary compare can take a real long time, do it only for image folders and catalog NOT preview folders.
2. AUTOMATIC: I use Bittorrent Sync, where I have setup a sync folder. The folders over the network keep themselves in sync automatically. It also has an auto archive and version control system - which has been useful for my work files (not LR or images sofar).
Note, if one thing is deleted, it is deleted everywhere with this method! Therefore I use only manual sync with my RAID10 6TB.
Why LR catalogs only? I do this for my project folders too. The bittorrent sync infact, even syncs over internet.