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Windows NT Disk Performance on Multiprocessor Hosts

Some users have seen a problem in a VMware Workstation virtual machine using IDE virtual disks on a multiprocessor host computer. The I/O issue is especially noticeable when the virtual machine is booting.

Note: Performance in Windows NT guest operating systems may also be affected by disk fragmentation on the host computer. For details, see Configuring and Maintaining the Host Computer.

Improving Performance

You may increase performance by enabling DMA (direct memory access) on the virtual hard disk's IDE channel in the virtual machine.

If you have a virtual disk and a DVD/CD-ROM attached as master and slave to the primary IDE controller (channel 0) and you want to enable DMA, power off the virtual machine and use the virtual machine settings editor (VM > Settings) to move the DVD/CD-ROM drive to the secondary IDE controller (channel 1) at IDE 1:0.

You can enable the DMA feature after you finish installing Windows NT. You must install Service Pack 6a. Download DMACHECK.EXE from the Microsoft Web site
support.microsoft.com/support/kb/articles/Q191/7/74.ASP) and run it.

Click the Enabled option for the IDE controller and channel configured for the virtual disk. Typically, this is channel 0 only, unless you have the virtual machine configured with multiple virtual disks and no virtual DVD/CD-ROM drive.

As noted above, you should not enable DMA on an IDE channel with a virtual DVD/CD-ROM drive attached.

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