22.7 Migrating from MC to LAN Cluster Interconnect (and vice versa)

One of the exciting new features of TruCluster Server version 5.1A is the LAN Cluster Interconnect. This functionality opens up far more systems to clustering and the benefits of Single System Image management (which means, for starters, that you only have to install the OS once, applications once, etc.). We'll show the steps required to migrate from a MEMORY CHANNEL Cluster Interconnect (CI) to a LAN CI. But first, let's review a few requirements.

The Cluster Interconnect LAN:

Must be private to the cluster members alone.
Can be direct or configured with hubs or switches but not both.
Must disable Spanning Tree Protocol on switch ports that connect to cluster members
Must configure the switches in a "fully redundant LAN cluster interconnect" so that there is no packet forwarding between them.
Must be 100Mbps or 1000Mbps full duplex throughout the configuration (including switches/hubs). Using the half-duplex option (hubs) is not recommended because of the limited performance of hub technology.
Must be configured such that there is at least one point-to-point path between each member.
Must not be configured with Link Aggregation (LAG).
Must not be configured with more than two switches between any two members.

22.7.1 Moving from MEMORY CHANNEL to LAN Cluster Interconnect

Say that you built your cluster at a pre-V5.1A version, upgraded to V5.1A, and now want to try out the LAN CI that you've heard so much about. The first thing you should do is take out the TruCluster Server Cluster LAN Interconnect manual provided by HP and look in Chapter 4 for the directions. These steps are covered thoroughly in the manual but we'll go over them briefly here.

To perform this switch from MC to LAN Interconnect, we obviously have to schedule some down time because we're making a radical change to the medium that the cluster uses to do a whole suite of communicating and in order to install and/or remove hardware:.

Shut down and power off each member.
Install the network adapters for the private CI LAN if they aren't already installed and set the NIC's mode at the console prompt. For example:
```
 >>> set ewa1_mode FastFD 
```
Configure any switches or hubs to be used.
Power up and boot each member using the generic kernel (genvmunix). (It will boot with MEMORY CHANNEL as the cluster interconnect.)
Build a new kernel with doconfig (8) on each member.
Copy (don't mv!) the new kernel into / on each member. See Chapter 12, section 12.2.1 for more information about copying in the new kernel.
Configure the network using ifconfig (8) as a private subnet (cluster members only) and test it to make sure it works before trying to use it as the cluster interconnect. (Don't configure the network using any of the network setup tools or by modifying /etc/rc.config because the test network configuration must not survive a reboot.)

Save a copy of each member's /etc/sysconfigtab and /etc/rc.config.

 # for i in 1 2 > do >    cp /.local../../member${i}/boot_partition/etc/sysconfigtab \ >       /.local../../member${i}/boot_partition/etc/sysconfigtab.ni >    cp /.local../../member${i}/etc/rc.config \ >       /.local../../member${i}/etc/rc.config.ni > done

Inspect each member's /etc/rc.config checking NETDEV_* and NRDEV_*. If either of these environment variables is associated with the LAN device to be used for the CI, you must edit these variables manually so that there is no interference with the LAN CI configuration during boot. (This step will probably be an issue only if you are reconfiguring NICs that the system had been using.)
Modify or add the clubase and ics_ll_tcp kernel subsystems similar to the following on each member:
```
 clubase: cluster_interconnect = tcp 
```
```
 ics_ll_tcp: ics_tcp_adapter0 = nr0 ics_tcp_nr0[0] = ee0 ics_tcp_nr0[1] = ee1 ics_tcp_inetaddr0 = 10.1.0.1 ics_tcp_netmask0 = 255.255.255.0 
```
If you are not using NetRAIN for the CI, you obviously will set the ics_tcp_adapter0 attribute to the value of "ee0", for example, and not include the ics_tcp_nr* entries. Refer to section 19.3.7.3 for details on modifying sysconfigtab.
Check the clubase:cluster_node_inter_name attribute.

If this was a cluster that was upgraded from an earlier version, the node name may contain "mc0"; if it does, change this to "ics0".

For example, change molari-mc0 to molari-ics0.
Edit the /etc/hosts file to reflect the new IP names and addresses of the LAN CI devices. Again, if this cluster was upgraded from an earlier release, you may have to change the "mc0" entries to "ics0" entries.
Change the CLUSTER_NET configuration variable to reflect the "ics0" name as well if it was upgraded from an earlier release. Use "rcmgr get CLUSTER_NET" to check it and "rcmgr set CLUSTER_NET <node>_ics0" to change it.
Shut down all members.
Boot each member.

22.7.2 Moving from LAN to MEMORY CHANNEL Cluster Interconnect

To convert your cluster from a LAN CI to a MEMORY CHANNEL CI, the process is similar but not quite as involved.

Shut down and power off each member.
Install the MEMORY CHANNEL hardware (including hubs if using hubs).
Power up and boot each member using the generic kernel (genvmunix). (It will boot with the LAN as the cluster interconnect.) Note that you could simply add the entry "config_driver mchan" to the kernel configuration file in the proper location (in /sys/conf/<HOSTNAME>) and rebuild the kernel instead of booting the generic kernel in this step.
Build a new kernel with doconfig on each member.
Copy (don't mv!) the new kernel into / on each member. See Chapter 12, section 12.2.1 for more information about copying the new kernel.

Save a copy of each member's /etc/sysconfigtab.

 # for i in 1 2 > do >   cp /.local../../member${i}/boot_partition/etc/sysconfigtab \ >      /.local../../member${i}/boot_partition/etc/sysconfigtab.ni > done

Modify the clubase kernel subsystem on each member, changing the cluster_interconnect attribute to "mct", and remove the ics_ll_tcp subsystem from sysconfigtab.
Shut down all members.
Boot each member.