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Description

AlphaServer supports up to a 3-nodes shared SCSI cluster for either OpenVMS cluster or TruCluster. That is, up to 3 AlphaServers can be daisy-chained to a set of shared SCSI devices. With Charon-AXP, we do this in a virtual way. The underlining hardware is not limited to KZPBA and HSZ controllers. A virtualized shared SCSI can run on any shared storage, include iSCSI, Fibre Channel, and Charon vdisks. Here we describe how to set up a shared SCSI environment.

Step-by-step guide

Requirement

            The shared SCSI can be built on a single PC server multiple Charon instances environment, or a multiple PC server environment.

            The requirement of configuring a shared SCSI on a single PC server multiple Charon instances for shared SCSI is basically the same as non-shared SCSI. A PC server with sufficient cores, memory, network ports and disk space to run all the instances is good enough.

            The requirement of configuring a shared SCSI on multiple PC servers is a little different. We still need sufficient cores, memory, network ports and disk space. In addition to these, we need to have:

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            Configuration in Charon is done in two parts - the virtual SCSI controller; and the SCSI disks. The sharing is done in the SCSI controller setting.

Configuring the shared SCSI controller

            Virtual shared SCSI buses are talked through network using TCP/IP. In Charon configuration, we have to specify the IP address and port (ie. an IP socket) for each virtual SCSI controller, so that other virtual SCSI controllers on the same bus can talk to it.

            The shared SCSI is defined like this:

set PKA port[600]=17016 host[600]="192.168.13.3:16017"

            Meaning:

PKA <== The SCSI bus is PKA

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:16017” <== The port that the remote system use is 16017, it will be defined in the remote system with “set port[700]=16017” which follows the same way above

            Here we have an example of a 3-node cluster, A, B and C. Each node got 3 shared SCSI controller PKA, PKB and PKC, and are running on 3 different PC servers. Below shows how they are configured according the above rule.

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Node C – IP address is 192.168.13.4

Node A, SCSI controller configuration

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• SCSI ids of the emulated SCSI controller are all 7

load KZPBA PKA scsi_id=7

set PKA port[600]=17016 host[600]="192.168.13.3:16017" <== point to node B

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set PKC port[500]=17216 host[500]="192.168.13.4:15217" <== point to node C

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Node B, SCSI controller configuration

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• SCSI ids of the emulated SCSI controller are all 6

load KZPBA PKA scsi_id=6

set PKA port[700]=16017 host[700]="192.168.13.2:17016" <== point to node A

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set PKC port[500]=16215 host[500]="192.168.13.4:15216" <== point to node B

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Node C, SCSI controller configuration

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• SCSI ids of the emulated SCSI controller are all 5

load KZPBA PKA scsi_id=5

set PKA port[700]=15017 host[700]="192.168.13.2:17015" <== point to node A

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            A picture will make this easy to understand.

 

Configuring the storage

            In the configuration of single PC server multiple instances, the shared storage can be a locally attached physical drive, from iSCSI, Fibre Channel, and also Charon virtual disks.

            The key point to configure shared SCSI disks in this configuration is to make sure the same DK device on different nodes are pointing to the same container.

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set PKA container[1]=”\\.\PhysicalDrive3” <== LUN 8

            Note that when the disks are presented to PC servers, the PhysicalDrive number of the same LUN may not be the same among different PC servers. It must be careful on that. In above, DKA0 is LUN 7, DKA100 is LUN 8. This is the same across all three hosts even the PhysicalDrive number in PC server B is different from the other two.

            To make this easy to manage, it is recommended to make the same PhysicalDrive number on different node point to the same LUN. Some simple guidelines are listed below:

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