Dynamic Partitioning For Virtual Ethernet Devices; Limitations And Considerations - IBM p5 590 System Handbook

The virtual Ethernet can also be used as a bootable device to allow such tasks
as operating system installations to be performed using Network Installation
Management (NIM).
Performance considerations
The transmission speed of virtual Ethernet adapters is in the range of 1-3
Gigabits per second, depending on the transmission (MTU) size. A partition can
support up to 256 virtual Ethernet adapters with each virtual Ethernet capable to
be associated with up to 21 VLANs (20 VID and 1 PVID).
The virtual Ethernet connections generally take up more processor time than a
local adapter to move a packet (DMA versus copy). For shared processor
partitions, performance will be gated by the partition definitions (for example
entitled capacity and number of processors). Small partitions communicating
with each other will experience more packet latency due to partition context
switching. In general, high bandwidth applications
small shared processor partitions. For dedicated partitions, throughput
comparable to a 1 Gigabit Ethernet for small packets providing much better
performance than 1 Gigabit Ethernet for large packets. For large packets, the
virtual Ethernet communication is copy bandwidth limited.
For more detailed information relating to virtual Ethernet performance
considerations refer to the following publication:
Advanced POWER Virtualization on IBM Sserver p5 Servers Architecture
and Performance Considerations, SG24-5768.

3.3.3 Dynamic partitioning for virtual Ethernet devices

Virtual Ethernet resources can be assigned and removed dynamically. On the
HMC, virtual Ethernet target and server adapters can be assigned and removed
from a partition using dynamic logical partitioning. The mapping between
physical and virtual resources on the Virtual I/O Server can also be done
dynamically.

3.3.4 Limitations and considerations

The following are limitations that must be considered when implementing an
virtual Ethernet:
A maximum of up to 256 virtual Ethernet adapters are permitted per partition.
Virtual Ethernet can be used in both shared and dedicated processor
partitions provided the partition is running AIX 5L Version 5.3 or Linux with the
appropriate kernel or a kernel that supports virtualization.
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