Oracle VM Server for SPARC - Oracle Solaris 10 System Virtualization Essentials - page 103

between 2 and 16: One CPU is added or removed at a time (the attack and decay
values). For example, if the CPU utilization exceeds 75%, a CPU is added unless
ldom1 already has 16 CPUs.
The resource manager provides flexible and powerful policy-driven dynamic
CPU resource management for Logical Domains that can automatically adjust
CPU assignments based on CPU resource requirements and domain priorities.
3.4.12 Cloning a Domain
The Logical Domains technology makes it easy to clone systems, especially when
using virtual disks residing in ZFS. A golden image instance of Oracle Solaris can
be installed, patched, and customized, and then used as a master copy for multiple
domains.
ZFS makes this process efficient by letting the administrator take a snapshot
of a virtual disk and then create clones from it. Snapshots are read-only images
of data in a ZFS file system at the time the zfs snapshot command is executed,
while clones are read/write images based on the snapshot. ZFS saves disk space
because only changed data takes up additional space on disk. For example, if a
snapshot is made of a ZFS file system with 100 GB of data and 5 MB of data is
changed, only 5 MB of additional disk space is consumed by the snapshot. Both
a snapshot and the file system it is based on use common disk locations for data
that is common to both. The same is true with clones: Space is consumed only
for changed disk contents. At first, the disk footprint of the new domain will be
negligible, as shown in the following example, but eventually it may increase if the
contents of the Solaris instance diverge from the master image.
Virtual disks based in a different file system, such as UFS, can be easily repli-
cated by using the low-tech cp command. With this approach, however, each copy
of a disk will require the same disk space as the original. Given that ZFS is much
more space efficient, it is the recommended technique for cloning a domain.
Before cloning a domain, be sure to shut it down to ensure that all buffers have
been written and that its disk contents are stable. You may also wish to unbind the
domain if its purpose is to be a template for other domains.
Then, assuming use of the same domain as in the previous example, we could
issue the following commands:
# zfs snapshot tank/ldoms/ldom1@initial
# zfs list
NAME USED AVAIL REFER MOUNTPOINT
…
rpool/ldoms/ldom1 2.52G 61.6G 2.52G /ldoms/ldom1
rpool/ldoms/ldom1@initial 0 - 2.52G -
continues