1.4 The IO Subsystem

     

The PCI IO subsystem has become the prevalent IO interface over the last few years due to its high capacity and industry-wide support. We are starting to see the use of the 64-bit 133MHZ PCI-X interface in our newest servers. On many HP servers running HP-UX 11i and using PCI interface cards, we now have access to a feature known as Online Addition and Replacement (OLA/R). This feature allows us to replace interface cards with the Operating System still running. If the affected card happens to interface with the root disk, replacing it can sometimes be a heart-stopping moment. If we can perform a successful Critical Resource Analysis, we will establish categorically that we have additional resources supporting access to the root disk even if we turn off the primary interface. This discussion encompasses such things a LVM PV Links and VxVM Dynamic Multi-Pathing. The subject areas of Volume Management are highly geared to those two critical concepts: performance and high availability . While on the subject of disks, volumes , filesystems, and devices, we can't forget about the emergence of Fibre Channel as an ever-increasing interface to our disks. Fibre Channel has some key influences in an entire solution as well as some major impacts in simple concepts such as the device file naming convention. We can't go into every intricacy of Fibre Channel here, but what we do discuss are the impacts on device files and how Fibre Channel can affect the implementation of our clustering solutions such as Serviceguard.