HP NetServer AA 4000 HP Netserver AA Solution Administrator's Guide v - Page 31

• Each IOP requires a licensed copy of the Windows operating system that should be accessed only to perform maintenance procedures. In addition to the concepts described in Chapter 1, the Endurance fault tolerant technology coordinates all I/O requests and responses between the CEs and IOPs using the ESIs and the IL, as shown in Figure 2-1. • In the Endurance server, the ESIs (Endurance System Interconnects) provide the interconnect paths for all Endurance server I/O requests and responses. These paths connect the IOPs to the CEs as follows: - ESI11 is the path from IOP1 to CE1. - ESI12 is the path from IOP1 to CE2. - ESI21 is the path from IOP2 to CE1. - ESI22 is the path from IOP2 to CE2. • The IL (IOP Link) is a dedicated private network for completing mirror copies (transferring mirrored disk data) between the IOPs, and for communication between the IOPs. The IL is physically supported by connecting two Ethernet adapters, one in each IOP. The ESI is the I/O data path between the CE and redirected devices on the IOPs. CE 1 CE 2 CE 1 CE 2 IOP 1 IOP 2 The IL is the mirror copy data path between the IOPs. CE 1 CE 2 IOP 1 IOP 2 Local Area Network Endurance System Interconnects (ESI) IOP 1 IOP 2 IOP Link (IL) Figure 2-1 Interconnect Paths in the Endurance Server Endurance Overview 2-3