Yesterday, VMware posted an article about a bug that can hang the Mac and corrupt the virtual machine. The company also offered a configuration change as a workaround until the bug is fixed. However, VMware previously stated that the Fusion 1.1.1 update dealt with this same problem and did not require the configuration change.

Yesterday's VMware article referred the bug as "an Apple problem with unbuffered IO," and said they have reported the problem to Apple. The VMware article said that to prevent freezing and data loss, users should go to VMware Fusion Preferences and select "Optimize for virtual machine disk performance." The company said that the problem can occur when Preferences are set to "Optimize for Mac OS application performance."

However, in January, VMware said that with the Fusion 1.1.1 update, this configuration setting was not necessary:

As a workaround for Apple bug 5679432 (Mac OS X hang under heavy disk load when unbuffered I/O is in use), VMware Fusion 1.1.1 disables unbuffered disk I/O on Mac OS X 10.5 hosts, even when the user selects Optimize for Mac OS application performance in VMware Fusion preferences.

We've had previous reports of VMware Fusion crashing in Leopard starting with version 1.1. In January, VMware reported to us that there was a conflict with Fusion and FileVault. A week later, VMware said that the 1.1.1 update fixed the FileVault issue. A reader reported that Mac OS X 10.5.3 update fixed the FileVault issue as well.

In another report today, we report that a reader believes that a bad RAM module was causing VMware to crash Leopard.

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