Novell SUSE Linux Enterprise Server, Manual

Page: 62 / 98

5.15 File-Backed Virtual Disks and
Loopback Devices
When a virtual machine is running, each of its file-backed virtual disks consumes a
loopback device on the host. By default, the host allows up to eight loopback devices
to be consumed.
To simultaneously run more file-backed virtual disks on a host, you can increase the
number of available loopback devices by adding the following option to the host’s
/etc/modprobe.conf.local
file.
options loop max_loop=x
where
x
is the maximum number of loopback devices to create.
Changes take effect after the module is reloaded.
TIP
Enter
rmmod loop
and
modprobe loop
to unload and reload the module.
In case
rmmod
does not work, unmount all existing loop devices or reboot the
computer.
5.16 Saving Virtual Machines
The save operation preserves the exact state of the virtual machine’s memory. The op-
eration is slightly similar to hibernating a computer. The virtual machine is off, but it
can be quickly restored to its previously-saved running condition. The operation does
not make a copy of any portion of the virtual machine’s virtual disk.
When saved, the virtual machine is paused, its current memory state saved to a location
you specify, and then the virtual machine is stopped. The amount of time to save the
virtual machine depends on the amount of memory allocated. When saved, a virtual
machine’s memory is returned to the pool of memory available on the host.
The restore operation is used to return a saved virtual machine to its original running
state.
56 Virtualization with Xen