Intel 170 Servers, AS/400 RISC Server manual IXS and IXA attached servers, ISCSI attached servers

IXS and IXA I/O operations (disk, tape, optical and virtual Ethernet) communications occur through the individual IXS and IXA IOP resource. This IOP imposes a finite capacity. The IOP processor utilization may be examined via the iSeries Collection Services utilities.

The performance results presented in the rest of this chapter are based on measurements and projections using standard IBM benchmarks in a controlled environment. The actual throughput or performance that any user will experience will vary depending upon considerations such as the amount of multiprogramming in the user's job stream, the I/O configuration, the storage configuration, and the workload processed. Therefore, no assurance can be given that an individual user will achieve throughput or performance improvements equivalent to the ratios stated here.

17.3 System i memory rules of thumb for IXS/IXA and iSCSI attached servers.

The i5/OS machine pool memory “rule of thumb” is generally to size the machine pool with at least twice the active machine pool reserved size. Automatic performance adjustments may alter this according to the active load characteristics. But, there are base memory requirements needed to support the hardware and set of adapters used by the i5/OS partition. You can refer to the System i sales manual or Work Load Estimator for estimates of these base requirements. The “rules of thumb” below estimates the additional memory required to support iSCSI and IXS/IXA.

17.3.1 IXS and IXA attached servers:

I/O occurs through fixed memory in the machine pool. The IXS and IXA attached servers require approximately an additional 4MBytes of memory per server in the machine pool.

17.3.2 iSCSI attached servers:

IBM Director Server is required in each i5/OS partition running iSCSI HBA targets. IBM Director requires a minimum of 500 Mbytes in the base pool.

The specific memory requirements of iSCSI servers vary based on many configuration choices, including the number of LUNs, number of iSCSI target HBAs, number of NWSDs, etc. A suggested minimum

memory “rule of thumb”11 is:

11Based on a rough configuration of 5 LUNS per server, 2 VE connections per server, and two target HBA connections per server.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
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