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Virtual Machine on USB or Other Slow Storage Device Runs Slowly

Details

I created a virtual machine on a USB storage device that reads and writes data more slowly than an internal hard drive. My virtual machine runs slowly. What can I do to improve the performance of this virtual machine?

Solution

By default, when a virtual machine is stored on a local device, VMware Workstation uses a file in the virtual machine's directory as a memory swap file. USB devices -- including flash memory drives, which read and write data much more slowly than internal hard drives -- are seen as local devices. When the memory swap file is on such a slow device, virtual machine performance suffers.
 
The same effect is seen with other types of slow local storage devices, such as Zip drives.  Another  symptom of this may be excessive disk I/O.
 
You can improve performance by changing a configuration setting so Workstation uses the host system's hard drive to store the swap data.
 
To do so, use a text editor to add the following line to the virtual machine's configuration (.vmx ) file:

mainMem.useNamedFile=FALSE
 
 
In some cases, the same thing can be seen where virtual machines are stored on other types of slow disk systems. If this is the case, there are some further settings that may help. First, go into the Host settings and adjust memory so that it is set to "Fit all virtual machine memory into reserved host RAM". (With Workstation, this could be done via Edit -> Preferences from the menu, with Server the same could be done via Host -> Settings.)
 
Note: Care should be taken with this. While it will reduce disk use for memory swapping, it will put more of a burden on host physical RAM. Make sure there is enough RAM on the host to support this.
 
Additionally, there are also some further .vmx settings that could be used - along with the same caution that implementing these can use more host physical RAM:

sched.mem.pshare.enable = "FALSE"
MemTrimRate = 0
prefvmx.useRecommendedLockedMemSize = "TRUE"
prefvmx.minVmMemPct = "100"


Special note for ACE Users: VMware recommends you use the Pocket ACE feature if planning to deploy to USB media. Deploying a Pocket ACE to removable media automatically optimizes for performance, so the above steps are NOT recommended with Pocket ACE.

Keywords

relnotes; 1620; WS500

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Actions
  • KB Article: 1620
  • Updated: Aug 14, 2009
  • Products:
    VMware ACE
    VMware Server
    VMware Workstation
  • Product Versions:
    VMware ACE 2.0.x
    VMware Server 1.0.x (Linux)
    VMware Workstation 5.x (Linux)
    VMware Workstation 5.x (Windows)
    VMware Workstation 6.x (Linux)
    VMware Workstation 6.x (Windows)