To understand how vPars works, compare it to a computer not
using vPars. Figure 2-1 shows a 4-way HP-UX computer. Without vPars,
all hardware resources are dedicated to one instance of HP-UX and
the applications that are running on this one instance.
Figure 2-2 shows the software stack where all applications
run on top of the single OS instance:
Using
vPars, you can allocate a computer's resources into two
or more virtual partitions, each with a subset
of the hardware. In Figure 2-3, two virtual partitions are shown,
each with its own boot disk, its own CPUs, its own LAN connection,
and a sufficient subset of memory to run HP-UX and the applications
intended to be hosted on that virtual partition.
Each application can run on top of separate OS instances.
Instead of a single OS instance owning all the hardware, the vPars
monitor manages the virtual partitions and their OS instances as
well as the assignment of hardware resources to each virtual partition.
vPars Monitor |
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The vPars monitor manages
the assignment of hardware resources to virtual partitions, boots
virtual partitions and their kernels, and emulates certain firmware
calls. By emulating these specific calls, vPars creates the illusion
to each HP-UX instance that it is running on a standalone computer,
consisting of the hardware that has been assigned to it.
Once a partition is launched, the monitor transfers ownership
of the hardware to the virtual partition. At that point the monitor
is not involved in accessing I/O hardware, physical memory, or process
to processor cycles: the individual HP-UX instances have complete ownership
of their respective hardware resources. This allows each partition
to run at full speed.
The commands for the vPars monitor are shown in the section “Using Monitor Commands”; however, most of
the vPars operations are performed using vPars commands at the UNIX
shell level. For more information on the commands, see the chapter Chapter 5 “Monitor and Shell Commands”.
Partition Database |
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At the heart of the vPars monitor is the partition
database. The partition database contains partition
configuration information. Using the partition database, the monitor
tracks which virtual partitions exist and what hardware resources
and partition attributes are associated with each partition.
When the monitor boots (see “Boot Sequence”), it reads a copy of the partition database
from a file, by default /stand/vpdb, on the same disk from which the monitor /stand/vpmon is booted. Then, the monitor creates a master copy of
the vPars partition database in the memory reserved by the monitor.
The operating system of each partition also keeps a local
copy of the partition database in a file, by default /stand/vpdb, on its local boot disk.
You can create, modify, and view the database contents using
vPars commands at the UNIX shell level. See Chapter 5 “Monitor and Shell Commands”. Because the format of the database is
proprietary, you must use only vPars commands to create, modify,
and view the database.
Whenever you execute a vPars command from the UNIX shell of
a partition, the change is made first to the monitor's
master copy. Then, the operating system from which you executed
the command updates its local copy from the master copy. Every five
seconds, the operating system of each running partition automatically
updates its local copy from the master copy. This synchronization
ensures that the partitions and changes to the partition database
are preserved when the entire computer is rebooted.
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 | NOTE: The monitor can only synchronize to the database files
of running partitions. If you reboot the computer, you should boot
the monitor from the boot disk of a partition that was running during
your most recent partition configuration change. |
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