I recently got the OWC Mercury On-The-Go Pro 1TB (one terabyte) drive to test. Before this drive I was carrying TWO external hard drives with me when I traveled. One was a clone backup of my internal drive. I swear by having a clone backup because I want the ability to "boot" from the external if my drive dies right before or during a presentation. Mac OS X's Time Machine is great, but since it's not bootable, there's no time to do a restore if something happens while on stage. The other drive contains files and videos that I may use from time to time during a presentation, but don't need to tie up my internal drive with. I also use that other drive to backup photos onto from a photo shoot in my studio until I get home.
The 1TB OWC Drive Replaces 2 of My External Drives
My goal for this drive was to use it to replace the two drives I'm currently carrying. I got the drive and partitioned it to 2 500GB partitions. The first partition I use to backup (clone) my internal drive via SuperDuper! The second 500GB partition is for those other misc files and temporary backups I travel with. Although I knew from a size perspective that the 1TB capacity would be exactly what I needed, I was concerned about the relatively slow speed of this drive. Most laptop 2.5" drives spin at either 7200 rpms or 5400 rpms. This drive spins at only 5200 rpms. Back in the day, some 2.5" drives were as slow as 4200 rpms. So while it's not the slowest drive on the planet, it is slower than the speeds regularly available in other capacities today. So for the choice was either carry two fast drives or one big slower drive.
After I did my clone backup and loaded on all the files I wanted to carry via the other partition, I did a boot test from this drive while it was connected via Firewire 800. It worked. While I could tell that it was slower than my internal 7200 rpm drive, it was tolerable. Keeping in mind that I would only be booting from this drive in an emergency anyway, I can live with the speed if it means carrying one less drive 100% of the time.
The Mercury On-The-Go Pro 3 in 1 enclosure
I've been a fan of this enclosure for years. Although there are certainly smaller, sleeker 2.5" drive enclosures out there, this enclosure has never failed me. I can connect via Firewire 800, 400 or USB 2. It's bus powered on all 3 ports and at a glance I can "see" exactly which drive is inside (make, model and capacity). I've had smaller enclosures overheat before and that's never been a problem for me with the Mercury On-The-Go Pro. The drive comes with all the cables you need, a carrying case and an Firewire 800-400 cable.
The 1TB Mercury On-The-Go Pro drive goes for $260 and you can get it here.
I recommend this particular model for someone who needs to carry around a lot of data and speed is not the most important factor. If you want a faster drive, look at their other models here. The folks over at OWC are GREAT to deal with and I also buy my RAM from them too. Never had any issues buying from them. They stand behind what they sell.