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Site Planning for Fault-Tolerant Systems
Site Planning for ftServer 2500, 4400, and 6200 Systems 1-3
installation site and moved the system to the site. For more information about the CAC,
see
Getting Help in the Preface or the http://www.stratus.com/support/cac/ Web site.
See Appendix A, “System Specifications” for the specifications of the base ftServer
systems and of PDUs. See the Stratus ftServer Systems: Peripherals Site
Planning Guide (R582) for specifications of other components.
Site Planning for Fault-Tolerant Systems
Consider the following specific fault-tolerant features of ftServer systems for site
planning:

Lockstep technology means that the systems contain redundant hardware. The
systems contain two enclosures, each containing a full computing environment that
consists of a CPU element and an I/O element.
If a component in a CPU element malfunctions, the corresponding CPU element in
the other enclosure, which is processing the same information in lockstep,
continues processing without interruption. If a component in the I/O element
malfunctions, the system fails operation over to the corresponding element in the
other enclosure and continues to operate normally. The only consequences are
that the system is less fault tolerant, and any I/O throughput distributed between
the enclosures may be reduced. To restore full fault tolerance, an enclosure can be
replaced without taking the system offline.

ftServer systems can connect to the ActiveService Network (ASN).
Connecting a system to the ASN allows the CAC or your authorized Stratus service
representative to remotely diagnose, troubleshoot, and resolve problems online.
To enable connectivity to the ASN, an ASN modem can be attached directly to the
system and managed by system software. In Windows or Linux systems, two
partnered Virtual Technician Modules (VTMs), if installed in the system, manage
the modem. The VTMs can also connect to the ASN through their Ethernet ports,
if the network to which they are attached has Internet access. Systems without
modems or VTMs can connect to the ASN through an Internet connection.
N O T E
ftSSS for VMware vSphere does not support VTMs.
Systems that connect to the ASN using partnered VTMs provide the highest level
of availability. VTMs provide ASN connectivity even when the operating system is
not operational. VTMs also allow internal administrators to remotely service the
system over a telephone line or IP network, regardless of the state of the operating
system.