Reasons to Partition a Hard Drive

Updated july, 2011

A question that often shows up on Mac forums is "Should I partition my hard drive?" Many users have strong opinions on this question and they're quick to answer with a definite no or definite yes, but I've noticed that it is rare for someone to explain why they respond as they do. Those against partitioning a hard drive usually say it's not necessary and those for it usually respond with "I do it." Clearly, those responses aren't very helpful to the person who posed the question. In this article, I give my reasons why I think partitioning a hard drive, especially an external hard drive, is a good idea.

Cloning

If you value your data and the work you do on your computer everyday, you should be cloning or backing up your boot drive on a regular basis. If you have a large internal drive that is not partitioned, cloning the drive, even with an incremental cloning option, can be time-consuming. I like to have a separate partition just for my system and essential software that must be placed in the Applications folder. I keep all other applications (i.e., most third-party applications) and all of my data on different partitions. This keeps my boot partition small (around 20 to 30 GB) and makes cloning on a daily basis quick and easy. Using the Smart update (incremental cloning) feature ofSuperDuper!, I can update my backup drive in 10 to 15 minutes.

Organization

As you use your computer, you'll probably start to accumulate hundreds and maybe thousands of files. Keeping everything organized on one drive can be a challenging and time-consuming task. I manage the myriad of files on my computer by keeping separate partitions for my system software and essential related files, third-party applications, data, and Time Machine. Although my data partition is not as neat as I would like it to be, at least I know that all of my data files are stored on just that partition.

Spotlight Searching

If you have ever tried to search a large hard drive, you know that the process can be slow, even with Spotlight. However, if you partition your drive, Spotlight searching really does become superfast, especially if you keep your partitions to reasonable sizes. For example, my data drive on my old PPC Mini includes my iTunes library and literally thousands of data files. I just did a test to see how fast it would find a particular song and Spotlight found the song in under a second.

Safety

Systems, even Mac OS X, can become corrupted and suddenly stop functioning. Sometimes the only solution to the problem is to erase the drive. If you have all of your data on that partition, erasing and restoring your drive can take a long time. Also, even if you cloned your drive, unless you did it immediately before the drive became corrupted, you might lose valuable data. Keeping data on a separate partition gives extra protection in the event of data corruption to a boot drive. Note that I'm not referring to drive failure due to mechanical problems with the drive - this reason applies only to data corruption on a drive.

Backup System

I like to keep a backup system on a separate partition in case my boot partition gets corrupted. In the event of data corruption on my boot drive, I can always boot into my emergency backup on the extra partition and see if Disk Utility can repair the boot drive. On my Intel Mac, I also keep Mac OS X 10.4 (Tiger) on one partition for the rare instances when I need to use an older application that is not compatible with Leopard. In the early, very "buggy" days of Leopard, that extra partition saved me time and frustration when I needed to revert back to Tiger.

Time Machine

If you use Mac OS X 10.5 or 10.6 and Time Machine, you know that Time Machine works better if the drive to which it is backing up is not used for other purposes. To use Time Machine effectively and use your backup drive wisely, partitioning the drive is the best solution. External backup drives are usually larger than internal drives and partitioning it will let you use all the space on the drive for a variety of purposes and not just for Time Machine. For example, on my Intel Mac, I have four partitions on my external hard drive - one for my system clone, one for my data clone, one as an emergency Mac OS X 10.4 system, and one just for Time Machine.

Whether you decide to partition your drive or not is up to you, but at least now you have some good explanations of why partitioning a drive might be a good idea.