Installation guide

Note
There are two methods for working around the para-virtualized device limit: using phy devices
(devices using the physical access mode) or using LVM on the guest.
A host has no limit to the number of phy devices it can have if it has sufficient resources.
LVM, or a similar logical partitioning tool, can be used on a block device to create additional
logical partitions on a single para-virtualized block device.
Xen Para- virt u aliz at io n limit at io n s
For x86 guests, a maximum of 16GB memory per guest.
For x86_64 guests, a maximum of 168GB memory per guest.
A maximum of 254 devices per guest.
A maximum of 15 network devices per guest.
Xen f u ll virt u aliz at io n limit at io n s
For x86 guests, a maximum of 16GB memory per guest.
A maximum of four virtualized (emulated) IDE devices per guest.
Devices using the para-virtualized drivers for fully-virtualized guests do not have this limitation.
Virtualized (emulated) IDE devices are limited by the total number of loopback devices supported
by the system. The default number of available loopback devices on Red Hat Enterprise Linux
5.11 is 8. That is, by default, all guests on the system can each have no more than 8 virtualized
(emulated) IDE devices.
For more information on loopback devices, their creation and use, see the Red Hat Knowledge
Solution 1721.
Note
The number of available loopback devices can be raised by modifying the kernel limit.
In the /etc/modprobe.conf file, add the following line:
options loop max_loop=64
Reboot the machine or run the following commands to update the kernel with this new limit:
# rmmod loop
# modprobe loop
⁠Chapt er 5. Virt ualizat ion limit at ions
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