The PowerVM platform is the family of technologies, capabilities, and offerings that delivers industry-leading virtualization for enterprises. It is the umbrella branding term for IBM Power processor-based server virtualization:
Ê IBM Power Hypervisor
Ê Logical partitioning
Ê IBM Micro-Partitioning®
Ê Virtual I/O Server (VIOS)
Ê Live Partition Mobility (LPM)
PowerVM is a combination of hardware and software enablement.
Note: PowerVM Enterprise Edition License Entitlement is included with each Power10 processor-based mid-range server. PowerVM Enterprise Edition is available as a hardware feature (#EPVV); supports up to 20 partitions per core, VIOS, multiple shared processor pools (MSPPs); and also offers LPM.
5.1.1 IBM Power Hypervisor
IBM Power processor-based servers are combined with PowerVM technology and offer the following key capabilities that can help to consolidate and simplify IT environments:
Ê Improve server usage and share I/O resources to reduce the total cost of ownership (TCO) and better use IT assets.
Ê Improve business responsiveness and operational speed by dynamically reallocating resources to applications as needed to better match changing business needs or handle unexpected changes in demand.
Ê Simplify IT infrastructure management by making workloads independent of hardware resources so that business-driven policies can be used to deliver resources that are based on time, cost, and service-level requirements.
Combined with features in the Power10 processor-based mid-range servers, the Power Hypervisor delivers functions that enable other system technologies, including logical partitioning technology, virtualized processors, IEEE virtual local area network (VLAN)-compatible virtual switches, virtual Small Computer Serial Interface (SCSI) adapters, virtual Fibre Channel (FC) adapters, and virtual consoles.
The Power Hypervisor is a basic component of the system’s firmware and offers the following functions:
Ê Provides an abstraction between the physical hardware resources and the LPARs that use them.
Ê Enforces partition integrity by providing a security layer between LPARs.
Ê Controls the dispatch of virtual processors to physical processors.
Ê Saves and restores all processor state information during a logical processor context switch.
Ê Controls hardware I/O interrupt management facilities for LPARs.
Ê Provides VLAN channels between LPARs that help reduce the need for physical Ethernet adapters for inter-partition communication.
Ê Monitors the enterprise Baseboard Management Controller (eBMC) and performs a reset or reload if needed, notifying the operating system (OS) if the problem is not corrected.
The Power Hypervisor is always active, regardless of the system configuration or whether it is connected to the managed console. It requires memory to support the resource assignment of the LPARs on the server. The amount of memory that is required by the Power Hypervisor firmware varies according to several factors:
Ê Memory usage for hardware page tables (HPTs)
Ê Memory usage to support I/O devices
Ê Memory usage for virtualization
Memory usage for hardware page tables
Each partition on the system includes its own HPT that contributes to hypervisor memory usage. The HPT is used by the OS to translate from effective addresses to physical real addresses in the hardware. This translation from effective to real addresses allows multiple OSs to run simultaneously in their own logical address space. Whenever a virtual processor for a partition is dispatched on a physical processor, the hypervisor indicates to the hardware the location of the partition HPT that can be used when translating addresses.
The amount of memory for the HPT is based on the maximum memory size of the partition and the HPT ratio. The default HPT ratio is 1/128th (for AIX, VIOS, and Linux partitions) of the maximum memory size of the partition. AIX, VIOS, and Linux use larger page sizes (16 and 64 KB) instead of using 4 KB pages. The use of larger page sizes reduces the overall number of pages that must be tracked; therefore, the overall size of the HPT can be reduced. For example, the HPT is 2 GB for an AIX partition with a maximum memory size of 256 GB.
When defining a partition, the maximum memory size that is specified is based on the amount of memory that can be dynamically added to the dynamic logical partition (DLPAR) without changing the configuration and restarting the partition.
In addition to setting the maximum memory size, the HPT ratio can be configured. The hpt_ratio parameter for the chsyscfg Hardware Management Console (HMC) command can be issued to define the HPT ratio that is used for a partition profile. The valid values are 1:32, 1:64, 1:128, 1:256, or 1:512.
Specifying a smaller absolute ratio (1/512 is the smallest value) decreases the overall memory that is assigned to the HPT. Testing is required when changing the HPT ratio because a smaller HPT might incur more CPU consumption because the OS might need to reload the entries in the HPT more frequently. Most customers choose to use the IBM provided default values for the HPT ratios.
Memory usage for I/O devices
In support of I/O operations, the hypervisor maintains structures that are called the translation control entities (TCEs), which provide an information path between I/O devices and partitions. The TCEs provide the address of the I/O buffer, indications of read versus write requests, and other I/O-related attributes. Many TCEs are used per I/O device, so multiple requests can be active simultaneously to the same physical device. To provide better affinity, the TCEs are spread across multiple processor chips or drawers to improve performance while accessing the TCEs.
For physical I/O devices, the base amount of space for the TCEs is defined by the hypervisor that is based on the number of I/O devices that are supported. A system that supports high-speed adapters also can be configured to allocate more memory to improve I/O performance. Linux is the only OS that uses these extra TCEs so that the memory can be freed for use by partitions if the system uses only AIX.
Ê Provides VLAN channels between LPARs that help reduce
the need for physical Ethernet adapters for inter-partition communication.
Ê Monitors the enterprise
Baseboard Management Controller
(eBMC) and performs a reset or
reload if needed, notifying the
operating system (OS) if the problem is not corrected.
The Power Hypervisor is always active, regardless of the system configuration or whether it is
connected to the managed console. It requires memory to support the
resource assignment of the LPARs on the server. The amount of memory that is required
by the Power Hypervisor firmware varies according to several
factors:
Ê Memory usage for hardware page tables
(HPTs) Ê Memory usage to support
I/O devices
Ê Memory usage for virtualization
Memory usage for hardware page tables
Each
partition on the system includes its own HPT that contributes to hypervisor
memory usage. The HPT is used by the
OS to translate from effective
addresses to physical real addresses in
the hardware. This translation from effective to real addresses allows
multiple OSs to run simultaneously in their own logical address space.
Whenever a virtual processor for a partition is dispatched on a physical
processor, the hypervisor indicates to the hardware
the location of the partition HPT
that can be used when translating
addresses.
The
amount of memory for the HPT is based
on the maximum memory size of the partition and the HPT ratio.
The default HPT ratio
is 1/128th (for AIX, VIOS, and Linux partitions) of the maximum
memory size of the partition. AIX, VIOS, and Linux use larger page sizes
(16 and 64 KB) instead of using 4 KB pages. The use of larger page sizes reduces the overall number of pages that must be tracked; therefore, the overall size
of the HPT can be reduced. For example, the HPT is 2 GB for an AIX partition with a maximum memory size
of 256 GB.
When defining
a partition, the maximum memory size that is specified
is based on the amount
of memory that can be dynamically
added to the dynamic logical partition (DLPAR) without changing
the configuration and restarting the
partition.
In addition to setting
the maximum memory size, the
HPT ratio can be configured. The
hpt_ratio parameter for the chsyscfg Hardware Management Console (HMC) command
can be issued to define
the HPT ratio that is used for a partition profile.
The valid values
are 1:32, 1:64, 1:128, 1:256, or 1:512.
Specifying a
smaller absolute ratio (1/512 is the smallest value) decreases the
overall memory that is assigned to
the HPT. Testing is required when changing the HPT ratio because
a smaller HPT might incur more CPU consumption
because the OS might need to reload the entries in the HPT more
frequently. Most customers choose to use the IBM
provided default values for the HPT
ratios.
Memory usage for I/O devices
In
support of I/O operations, the hypervisor
maintains structures that are
called the translation control entities (TCEs), which provide an
information path between I/O devices and partitions. The TCEs provide the address of the I/O buffer, indications of read versus write requests, and other I/O-related attributes. Many TCEs are used per I/O device, so multiple requests can be active
simultaneously to the same physical device.
To provide better
affinity, the TCEs are spread across multiple processor chips or drawers to improve performance
while accessing the TCEs.