![]() The basic concept behind this technique has been around for decades, and yet it is something that I almost never hear anyone mention. The biggest caveat, in this case, is that the technique that I am about to show you is ideally suited to lab VMs, but this probably isn’t the sort of thing that you would want to do in production. Like all miracle solutions, however, there are a few caveats. A boost for temporary VMsīut what if there was an easy way to make the VM perform far better, on the same hardware? Believe it or not, it is possible to give a poorly performing VM really good performance without upgrading the hardware. When you throw in the fact that this particular VM was running a really I/O intensive workload, it quickly becomes apparent why the VM performed so slowly. The VMs were running on aging lab hardware, which was a little bit slow to begin with. Of course, I can’t say that I was surprised. ![]() Although I got the job done, one of the virtual machines’ performance could be best described as painfully slow. The Power Macintosh G3 cannot start up from RAM disks.Recently, I had to set up a few virtual machines for use with one of the other articles that I was working on.The Macintosh Quadra 950 cannot use RAM disks if 256 MB (the upper limit) of RAM is installed.After a restart, the settings will take effect. On a System 7 or later Mac, proceed to the Memory control panel, and turn RAM disk off. The contents of the RAM disk must be copied and saved back on to the hard drive, and the RAM disk must be completely empty, before the Mac will allow you to resize the RAM disk.Ī RAM disk can be deleted only when all contents have been moved onto a hard drive or other device, leaving the RAM disk completely empty. If ! test -e /Volumes/\"ram disk\" thenĭiskutil erasevolume HFS+ \"ram disk\" `hdiutil attach -nomount ram://4629672` Since after each restart the ram disk is lost, the following AppleScript application can be used as a login item to make a new one: The following command creates the largest ram disk possible on Tiger, 2.2 GB:ĭiskutil erasevolume HFS+ "ram disk" `hdiutil attach -nomount ram://4629672` On Mac OS X a ram disk can be created using the shell. Select your desired size (not too big!), and restart. On a System 7 or later Mac, proceed to the Memory control panel, and activate the RAM disk option. Portables reported a higher rate of data survival on RAM disks than desktops. On other classic Mac models, data in the RAM disk can survive restarts and sleep, and is lost only when the Mac is completely shut down. A few Macintosh models, such as the Macintosh Portable and PowerBook 100, use static or low power RAM that are capable of retaining their contents while shut down, as long as the battery retains some power. ![]() Because Mac OS X handled RAM disks through the operating system instead of firmware, restarts would not preserve the contents in memory.ĭata, when copied to a RAM disk, is subject to volatility - as it is in memory instead of written to disk, some users fear that a crash would cause such data to vanish. Mac OS X only supported RAM disks from command-line tools. RAM disks on MacsĬlassic Mac OS used to support RAM disks by means of the Memory control panel. Improved performance of solid-state drives have decreased the usefulness of RAM drives in newer systems. In some cases, it is possible for the data to survive a restart which does not interrupt power to the computer's memory. Unlike a real drive, a RAM drive would lose such stored data when most computers are turned off. The program sets aside a user-definable block of RAM to be used as a drive, which can store and access files at far greater speeds than mechanical storage media.
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