VirtualBox

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doc/manual: Draft of section on improving network performance (#5582)

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1<?xml version="1.0" encoding="UTF-8"?>
2<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
3"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
4<chapter id="KnownIssues">
5 <title>Known limitations</title>
6 <sect1 id="ExperimentalFeatures">
7 <title>Experimental Features</title>
8 <para>Some VirtualBox features are labeled as experimental. Such
9 features are provided on an "as-is" basis and are not formally
10 supported. However, feedback and suggestions about such features are
11 welcome. A comprehensive list of experimental features follows:</para>
12 <itemizedlist>
13 <listitem>
14 WDDM Direct3D video driver for Windows guests
15 </listitem>
16 <listitem>
17 Hardware 3D acceleration support for Windows, Linux, and Solaris
18 guests
19 </listitem>
20 <listitem>
21 Hardware 2D video playback acceleration support for Windows
22 guests
23 </listitem>
24 <listitem>
25 PCI pass-through (Linux hosts only)
26 </listitem>
27 <listitem>
28 Mac OS X guests (Mac hosts only)
29 </listitem>
30 <listitem>
31 ICH9 chipset emulation
32 </listitem>
33 <listitem>
34 EFI firmware
35 </listitem>
36 <listitem>
37 Host CD/DVD drive pass-through
38 </listitem>
39 <listitem>
40 Support of iSCSI via internal networking
41 </listitem>
42 <listitem>
43 Synthetic CPU reporting
44 </listitem>
45 </itemizedlist>
46 </sect1>
47 <sect1 id="KnownProblems">
48 <title>Known Issues</title>
49 <para>The following section describes known problems with VirtualBox
50 $VBOX_VERSION_STRING. Unless marked otherwise, these issues are planned to
51 be fixed in later releases.</para>
52
53 <itemizedlist>
54 <listitem>
55 <para>The following <emphasis role="bold">Guest SMP (multiprocessor)
56 limitations</emphasis> exist:<itemizedlist>
57 <listitem>
58 <para><emphasis role="bold">Poor performance</emphasis> with
59 32-bit guests on AMD CPUs. This affects mainly Windows and Solaris
60 guests, but possibly also some Linux kernel revisions. Partially
61 solved in 3.0.6 for 32 bits Windows NT, 2000, XP and 2003 guests.
62 Requires 3.0.6 or higher Guest Additions to be installed.</para>
63 </listitem>
64
65 <listitem>
66 <para><emphasis role="bold">Poor performance</emphasis> with
67 32-bit guests on certain Intel CPU models that do not include
68 virtual APIC hardware optimization support. This affects mainly
69 Windows and Solaris guests, but possibly also some Linux kernel
70 revisions. Partially solved in 3.0.12 for 32 bits Windows NT,
71 2000, XP and 2003 guests. Requires 3.0.12 or higher Guest
72 Additions to be installed.</para>
73 </listitem>
74 </itemizedlist></para>
75 </listitem>
76
77 <listitem>
78 <para><emphasis role="bold">64-bit guests on some 32-bit host systems
79 with VT-x</emphasis> can cause instabilities to your system. If you
80 experience this, do not attempt to execute 64-bit guests. Refer to the
81 VirtualBox user forum for additional information.</para>
82 </listitem>
83
84 <listitem>
85 <para>For <emphasis role="bold">basic Direct3D support in Windows
86 guests</emphasis> to work, the Guest Additions must be installed in
87 Windows "safe mode". Press F8 when the Windows guest is booting and
88 select "Safe mode", then install the Guest Additions. Otherwise Windows'
89 file protection mechanism will interfere with the replacement DLLs
90 installed by VirtualBox and keep restoring the original Windows system
91 DLLs. <note>
92 <para>This does <emphasis role="bold">not</emphasis> apply to the
93 experimental WDDM Direct3D video
94 driver available for Vista and Windows 7 guests shipped with
95 VirtualBox 4.1.</para>
96 </note></para>
97 </listitem>
98
99 <listitem>
100 <para><emphasis role="bold">Guest control.</emphasis> On Windows guests,
101 a process lauched via the guest control execute support will not be able
102 to display a graphical user interface <emphasis>unless</emphasis> the
103 user account under which it is running is currently logged in and has a
104 desktop session.</para>
105
106 <para>Also, to use accounts without or with an empty password, the
107 guest's group policy must be changed. To do so, open the group policy
108 editor on the command line by typing
109 <computeroutput>gpedit.msc</computeroutput>, open the key
110 <emphasis>Computer Configuration\Windows Settings\Security
111 Settings\Local Policies\Security Options</emphasis> and change the value
112 of <emphasis>Accounts: Limit local account use of blank passwords to
113 console logon only</emphasis> to <emphasis>Disabled</emphasis>.</para>
114 </listitem>
115
116 <listitem>
117 <para><emphasis role="bold">Compacting virtual disk images is limited to
118 VDI files.</emphasis> The <code>VBoxManage modifyhd --compact</code>
119 command is currently only implemented for VDI files. At the moment the
120 only way to optimize the size of a virtual disk images in other formats
121 (VMDK, VHD) is to clone the image and then use the cloned image in the
122 VM configuration.</para>
123 </listitem>
124
125 <listitem>
126 <para><emphasis role="bold">OVF import/export:</emphasis><itemizedlist>
127 <listitem>
128 <para>OVF localization (multiple languages in one OVF file) is not
129 yet supported.</para>
130 </listitem>
131
132 <listitem>
133 <para>Some OVF sections like StartupSection,
134 DeploymentOptionSection and InstallSection are ignored.</para>
135 </listitem>
136
137 <listitem>
138 <para>OVF environment documents, including their property sections
139 and appliance configuration with ISO images, are not yet
140 supported.</para>
141 </listitem>
142
143 <listitem>
144 <para>Remote files via HTTP or other mechanisms are not yet
145 supported.</para>
146 </listitem>
147 </itemizedlist></para>
148 </listitem>
149
150 <listitem>
151 <para>Neither <emphasis role="bold">scale mode</emphasis> nor <emphasis
152 role="bold">seamless mode</emphasis> work correctly with guests using
153 OpenGL 3D features (such as with compiz-enabled window managers).</para>
154 </listitem>
155
156 <listitem>
157 <para>Preserving the aspect ratio in scale mode works only on Windows
158 hosts and on Mac OS X hosts.</para>
159 </listitem>
160
161 <listitem>
162 <para>On <emphasis role="bold">Mac OS X hosts,</emphasis> the following
163 features are not yet implemented:</para>
164
165 <para><itemizedlist>
166 <listitem>
167 <para>Numlock emulation</para>
168 </listitem>
169
170 <listitem>
171 <para>CPU frequency metric</para>
172 </listitem>
173
174 <listitem>
175 <para>Memory ballooning</para>
176 </listitem>
177 </itemizedlist></para>
178 </listitem>
179
180 <listitem>
181 <para><emphasis role="bold">Mac OS X guests:</emphasis>
182 <itemizedlist>
183 <listitem>
184 <para>Mac OS X guests can only run on a certain host hardware.
185 For details about license and host hardware limitations, please
186 see <xref linkend="intro-macosxguests" /> and check the Apple
187 software license conditions.</para>
188 </listitem>
189
190 <listitem>
191 <para>VirtualBox does not provide Guest Additions for Mac OS X
192 at this time.</para>
193 </listitem>
194
195 <listitem>
196 <para>The graphics resolution currently defaults to 1024x768 as
197 Mac OS X falls back to the built-in EFI display support. See
198 <xref linkend="efividmode" /> for more information on how to
199 change EFI video modes.</para>
200 </listitem>
201
202 <listitem>
203 <para>Even when idle, Mac OS X guests currently burn 100% CPU.
204 This is a power management issue that will be addressed in a
205 future release.</para>
206 </listitem>
207
208 <listitem>
209 <para>Mac OS X guests only work with one CPU assigned to the
210 VM. Support for SMP will be provided in a future release.</para>
211 </listitem>
212
213 <listitem>
214 <para>Depending on your system and version of Mac OS X, you
215 might experience guest hangs after some time. This can be fixed
216 by turning off energy saving (set timeout to "Never") in the
217 system preferences.</para>
218 </listitem>
219
220 <listitem>
221 <para>By default, the VirtualBox EFI enables debug output of the
222 Mac OS X kernel to help you diagnose boot problems. Note that
223 there is a lot of output and not all errors are fatal (they
224 would also show on your physical Mac). You can turn off these
225 messages by issuing this command:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" " "</screen>To
226 revert to the previous behavior, use:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" ""</screen></para>
227 </listitem>
228 </itemizedlist></para>
229 </listitem>
230
231 <listitem>
232 <para><emphasis role="bold">Solaris hosts:</emphasis> <itemizedlist>
233 <listitem>
234 <para>There is no support for USB devices connected to Solaris 10
235 hosts.</para>
236 </listitem>
237
238 <listitem>
239 <para>USB support on Solaris hosts requires Solaris 11 version
240 snv_124 or higher. Webcams and other isochronous devices are known
241 to have poor performance.</para>
242 </listitem>
243
244 <listitem>
245 <para>No ACPI information (battery status, power source) is
246 reported to the guest.</para>
247 </listitem>
248
249 <listitem>
250 <para>No support for using wireless adapters with bridged
251 networking.</para>
252 </listitem>
253
254 <listitem>
255 <para>Crossbow based bridged networking on Solaris 11 hosts does
256 not work directly with aggregate links. However, you can manually
257 create a VNIC (using <computeroutput>dladm</computeroutput>) over
258 the aggregate link and use that with a VM. This technical
259 limitation between VirtualBox and Solaris will be addressed in a
260 future release.</para>
261 </listitem>
262 </itemizedlist></para>
263 </listitem>
264
265 <listitem>
266 <para><emphasis role="bold">Guest Additions of version 4.1, 4.1.2 and 4.1.4 for Windows</emphasis>
267 Thus VirtualBox WDDM Video driver may be installed and kept in guest system
268 if Guest additions uninstallation is performed.
269 This is caused by a bug in Guest Additions uninstaller.
270 <note>
271 <para>This does <emphasis role="bold">not</emphasis> apply to Guest Additions update,
272 i.e. installing a one version of Guest Additions on top of another works correctly.</para>
273 </note>
274 To solve this problem, one should uninstall the VirtualBox WDDM Video driver manually.
275 To do that open Device Manager, and check whether the Display Adapter is named
276 "VirtualBox Graphics Adapter ..". If no - there is nothing to be done. If yes - right-clik
277 the VirtualBox Graphics Adapter in Device Manager, select "Uninstall", check "Delete the driver software for this device"
278 and click "OK". Once uninstallation is done - in Device Manager go to menu "Action" and select
279 "Scan for hardware changes" to make the propper (Windows default) driver be picked up for the Graphics adapter.
280 </para>
281 </listitem>
282
283 <listitem>
284 <para>Neither <emphasis>virtio</emphasis> nor <emphasis>Intel PRO/1000
285 </emphasis> drivers for <emphasis role="bold">Windows XP guests
286 </emphasis> do not support segmentation offloading. Therefore
287 Windows XP guests have slower transmission rates comparing to other
288 guest types. Refer to MS Knowledge base article 842264 for additional
289 information.</para>
290 </listitem>
291
292 <listitem>
293 <para><emphasis role="bold">Guest Additions for OS/2.</emphasis> Shared
294 folders are not yet supported with OS/2 guests. In addition, seamless
295 windows and automatic guest resizing will probably never be implemented
296 due to inherent limitations of the OS/2 graphics system.</para>
297 </listitem>
298 </itemizedlist>
299 </sect1>
300</chapter>
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