Sun Microsystems VIRTUALBOX VERSION 3.1.0_BETA2 - Manual (Page 161)

11 Troubleshooting
Certain applications may disable this key against Microsoft’s advice. If it is set to 0,
change it to 1 and reboot your system. VirtualBox relies on Windows notifying it of
media changes.
11.4.3 Sluggish response when using Microsoft RDP client
If connecting to a Virtual Machine via the Microsoft RDP client (called Remote Desktop
Connection), there can be large delays between input (moving the mouse over a menu
is the most obvious situation) and output. This is because this RDP client collects input
for a certain time before sending it to the VRDP server built into VirtualBox.
The interval can be decreased by setting a Windows registry key to smaller values
than the default of 100. The key does not exist initially and must be of type DWORD.
The unit for its values is milliseconds. Values around 20 are suitable for low-bandwidth
connections between the RDP client and server. Values around 4 can be used for a
gigabit Ethernet connection. Generally values below 10 achieve a performance that is
very close to that of the local input devices and screen of the host on which the Virtual
Machine is running.
Depending whether the setting should be changed for an individual user or for the
system, either
HKEY_CURRENT_USER\Software\Microsoft\Terminal Server
Client\Min Send Interval
or
HKEY_LOCAL_MACHINE\Software\Microsoft\Terminal Server
Client\Min Send Interval
can be set appropriately.
11.4.4 Running an iSCSI initiator and target on a single system
Deadlocks can occur on a Windows host when attempting to access an iSCSI target
running in a guest virtual machine with an iSCSI initiator (e.g. Microsoft iSCSI Ini-
tiator) that is running on the host. This is caused by a flaw in the Windows cache
manager component, and causes sluggish host system response for several minutes,
followed by a “Delayed Write Failed” error message in the system tray or in a sepa-
rate message window. The guest is blocked during that period and may show error
messages or become unstable.
Setting the environment variable VBOX_DISABLE_HOST_DISK_CACHE to 1 will
enable a workaround for this problem until Microsoft addresses the issue. For example,
open a command prompt window and start VirtualBox like this:
set VBOX_DISABLE_HOST_DISK_CACHE=1
VirtualBox
While this will decrease guest disk performance (especially writes), it does not affect
the performance of other applications running on the host.
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