Easily create a RAM disk for disk-intensive applications


Dec 7, 2011
Miami, Florida
Until yesterday, I never knew how easy it is to create a RAM disk on OS X. You don't even need a separate app.

Here is an excerpt from an article for those who may be unfamiliar with the concept of a RAM disk, followed by a link to the entire article:

Article by Jim Tanous at TekRevue

RAM Disks, as the name indicates, are logical storage volumes created using a computer’s memory (RAM) instead of a traditional hard drive or solid state drive. The benefits are easy to understand: RAM operates at speeds far beyond current hard drive technology. But there’s also a major negative: data stored in RAM is not persistent, meaning that it is erased when the RAM loses power due to a reboot, shutdown, or power loss.

Despite this drawback, there are still several situations that can greatly benefit from the speed of a RAM Disk, including using it as a Photoshop scratch area, manipulating large video files, or testing complicated databases. If you’ve got good backups of your data and you’re willing to risk losing the contents of a RAM Disk in the event of a power failure, setting one up is easy and fun. Here’s how.

I've gone ahead and calculated the valuex of XXXXX you need to use in the command line mentioned in the article for various sizes of RAM disks:

Screen Shot 2014-04-08 at 3.29.06 PM.png

Note that the Terminal app in OS X stores a history of recently used commands, and the history does not get erased even after a reboot. So once you enter the command once, you can access it again the following day by using the Up arrow right after you enter the Terminal... unless you're a heavy user of the Terminal app and you've entered hundreds of commands since.

The RAM disk is definitely not a new concept. I remember I used to work with a RAM disk ages ago on my Atari 130XE - a computer which came with 128 KB of RAM, but was only able to address 64 KB of RAM at a time due to the limits of the MOS 6502 processor it came with. You could use the extra 64 KB of RAM to create a RAM disk, or access the extra RAM via bank switching.
Last edited: