Creating RAM disk in macOS

macos-ramdisk.md

Built-in

diskutil erasevolume HFS+ 'RAM Disk' `hdiutil attach -nobrowse -nomount ram://XXXXX`

where XXXXX is the size of the RAM disk in terms of memory blocks.

Notes:

$2048$ memory blocks correspond to 1MB. Thus, XXXXX = YYYY * 2048 where YYYY is the size in MB.

E.g.

• ram://2048 will create 1MB RAM disk
• ram://2097152 --> 1 GB
• ram://4194304 --> 2 GB
• ram://8388608 --> 4 GB

Third-party Tools

• TmpDisk:: Open Source RAM disk management app.
• Ultra RAM Disk installs as a menu bar item that allows you to create RAM disks when needed.
• RAMDisk: is an app for creating as well as backing up RAM disks, to allow you to save their contents as well as restore RAM disks when you restart your Mac.
• RAMDiskCreator

Resources

• https://bogner.sh/2012/12/os-x-create-a-ram-disk-the-easy-way/
• https://blog.macsales.com/46348-how-to-create-and-use-a-ram-disk-with-your-mac-warnings-included
• https://www.jakobstoeck.de/2017/ramdisk-for-faster-applications-under-macos/

Update in 2021: it seems that TmpDisk is the only GUI option now. At least, for me.

In order to unmount such disk I use diskutil unmount /dev/rdisk3 then diskutil unmountDisk /dev/disk3. Is this a correct way?

@kvaDrug. hdiutil detach /dev/disk2 works for me

@kvaDrug. hdiutil detach /dev/disk2 works for me

diskutil erasevolume HFS+ 'RAM Disk' disk0 `hdiutil detach /dev/disk0 -nobrowse -nomount ram://33554415`

thats true ?

use APFS instead of HFS+, you may gain a better performance(based on test with Blackmagic)

The same for xonsh shell:

diskutil erasevolume HFS+ 'myramdisk' @$(hdiutil attach -nobrowse -nomount ram://@(2097152*1))
ls /Volumes/myramdisk
hdiutil detach @($(df | grep ram1g).split(' ')[0])