Another option, if you have a copy of Parallels Desktop or VMWare Fusion, is to install the Yosemite beta on a virtual machine. Although these tools are typically used to create virtual machines running Windows, they do support other operating systems, including OS X, meaning you can create a virtual Mac and install the Yosemite beta on it. That also reduces -- but doesn't entirely remove -- the risk of problems. If you go this route, you'll want to disable any features that allow the virtual machine to exchange files with your physical Mac to minimize potential data loss if there's a file system issue.
6. Back up any Mac before installing the beta
Whatever Mac you install the Yosemite beta on, and no matter how you install it, you should ensure that you have a complete and functional backup before beginning, even if you are installing on an alternate drive or into a virtual machine. You should also perform regular backups during your testing period. And you should store a known good backup -- disconnected from your Mac -- while testing because a file system issue could damage the data on your backup drive. Ideally, you'll use a second backup drive to perform any regular backups of your Mac while running the Yosemite beta.
7. Think carefully before using iCloud or third-party sync solutions
The risk of data loss isn't restricted to data on your Mac: iCloud data sync among multiple Apple products and third-party cloud services like Dropbox or Google Drive allow your Mac to work with and alter data in the cloud and on other Macs, PCs or mobile devices. You should carefully consider whether you want to risk changes or loss of data maintained or synced through such services. If you decide to use them on a Mac running the beta, you should ensure you have a known good copy of that data separate from the version of the data in the cloud.
Apple explicitly states that documents stored in iCloud will be updated by the Yosemite beta and will only be able to be synced with other Macs running the Yosemite beta (and eventually Yosemite's final release, as well as iOS 8).
Apple exec Craig Federighi announcing Apple's first public beta test for an OS in 14 years. (Image: Apple.)
8. Battery life may be compromised on portable Macs
If you're installing the beta on a laptop, you may notice that power management and battery life don't function normally. This could result in your battery discharging faster than it does when you're running Mavericks or other versions of OS X. This is a common occurrence with operating system betas across platforms. If you are going to be working on the go, you should ensure that you have a power adapter with you, and you may want to observe what, if any, impact the beta has on your MacBook's battery for a day or two after installing it before embarking on any travel.
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