Intel 170 Servers User Manual
The blue square line shows an iSCSI connection with a single target iSCSI HBA - single initiator iSCSI
HBA connection, configured to run with standard frames. The pink circle line is a single target iSCSI
HBA to multiple servers and initiators running also running with standard frames. With the initiators and
HBA connection, configured to run with standard frames. The pink circle line is a single target iSCSI
HBA to multiple servers and initiators running also running with standard frames. With the initiators and
switches configured to use 9k jumbo frames, a 15% to 20% increase in upper capacity is demonstrated.
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17.6 Virtual Ethernet CPU Cost and Capacities
If the virtual Ethernet connections are used for any significant LAN traffic, you need to account for
additional System i CPU requirements. There is no single rule of thumb applicable to network traffics, as
there are a great number of variables involved.
additional System i CPU requirements. There is no single rule of thumb applicable to network traffics, as
there are a great number of variables involved.
The charts below demonstrate approximate capacity for single TCP/IP connections, and illustrates the
minimum CPW impacts for some network transaction sizes (send/receive operations) and types gathered
with the Netperf
minimum CPW impacts for some network transaction sizes (send/receive operations) and types gathered
with the Netperf
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exerciser. The CPW chart below gives CPWs per Mbit/sec for increasing transaction
sizes. When the transaction size is small, the CPW requirements are greater per transaction. When the
arrival rate is high enough, some consolidation of operations within the process stream can occur and
increase efficiency of operations.
arrival rate is high enough, some consolidation of operations within the process stream can occur and
increase efficiency of operations.
Several charts are presented comparing the virtual ethernet capacity and costs between an iSCSI server
running jumbo frames and standard frames, and a IXS or IXA server. In addition, a comparison of costs
while using external NICs is added, to place the measurements in context. The “Point-to-Point” refers to
the cost between an iSCSI, IXS or IXA attached server and an host system across the point to point
connection. “Port Based VE” refers to a port-based connection between two guest servers in the same
partition. “VLAN based VE” refers to a Virtual LAN based connection between two guest servers in the
same partition, but using the VLAN to port associated virtual adapters. In the latter two cases, the total
CPW cost would be split across partitions if the communication would occur between guest servers
running jumbo frames and standard frames, and a IXS or IXA server. In addition, a comparison of costs
while using external NICs is added, to place the measurements in context. The “Point-to-Point” refers to
the cost between an iSCSI, IXS or IXA attached server and an host system across the point to point
connection. “Port Based VE” refers to a port-based connection between two guest servers in the same
partition. “VLAN based VE” refers to a Virtual LAN based connection between two guest servers in the
same partition, but using the VLAN to port associated virtual adapters. In the latter two cases, the total
CPW cost would be split across partitions if the communication would occur between guest servers
hosted by different partitions
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.
17.6.1 VE Capacity Comparisons
In general, VE has less capacity than an external Gigabit NIC. Greater capacity with VE is possible using
9k jumbo frames than with using standard 1.5k frames. Also, the iSCSI connection has a greater capacity
9k jumbo frames than with using standard 1.5k frames. Also, the iSCSI connection has a greater capacity
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
©
Copyright IBM Corp. 2008
Chapter 17 - Integrated BladeCenter and System x Performance
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Netperf TCP_STREAM
measured on a System i Model 570 - 2-way 26F2 processor (7495 capacity card), rated at
6350 CPWs, V5R4 release of i5/OS. The IXA attached server was a x365xSeries (4way 2.5Ghz Xeon with IXA
and Windows Server 2003 with SP1. The iSCSI servers were HS20 BladeCenter 32.Ghz uniprocessor servers
with a copper iSCSI (p/n 26K6489) daughter card. Switches were Nortel L2/3 Ethernet (p/n 26K6524)
and Windows Server 2003 with SP1. The iSCSI servers were HS20 BladeCenter 32.Ghz uniprocessor servers
with a copper iSCSI (p/n 26K6489) daughter card. Switches were Nortel L2/3 Ethernet (p/n 26K6524)
. This is
only a rough indicator for capacity planning, actual results may differ for other hardware configurations.
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Note that the Netperf benchmark consists of C programs which use a socket connection to read and write data
between buffers. The CPW results above don’t attempt to factor out the minimal application CPU cost. That is,
the CPW results above include the primitive Netperf application, socket, TCP, and Ethernet operation costs. A
real user application will only have this type of processing as a percentage of the overall workload.
between buffers. The CPW results above don’t attempt to factor out the minimal application CPU cost. That is,
the CPW results above include the primitive Netperf application, socket, TCP, and Ethernet operation costs. A
real user application will only have this type of processing as a percentage of the overall workload.
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In addition, jumbo frame configuration has no effect on the CPW cost of iSCSI disk operations.