To understand how vPars works, compare it to a server not
using vPars. Figure 2-1 shows a 4-way HP-UX server. 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 server'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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For each hard partition,
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 server, consisting of the hardware
that has been assigned to it.
Once a virtual 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”.
vPars
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 on the same disk from which the monitor /stand/vpmon is booted. The default file is /stand/vpdb. Then, the monitor creates a master copy of the vPars
partition database in the memory reserved by the monitor.
The operating system of each virtual 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 virtual partitions and changes to the partition
database are preserved when the entire hard partition is rebooted.
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 | NOTE: The monitor can only synchronize to the database files
of running virtual partitions. If you reboot the hard partition,
you should boot the monitor from the boot disk of a virtual partition
that was running during your most recent partition configuration
change. |
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