CHARON-VAX for Linux DSSI cluster
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- Bruno Miretti (Deactivated)
Table of Contents
Introduction
This section will describe how to configure DSSI cluster in CHARON-VAX for Linux.
General description
The DSSI storage subsystem for the CHARON VAX 4000 106, 108, 700 and 705 models is based on the emulation of "SHAC" host adapters. Routing of SCS cluster information among the emulated "SHAC" host adapters of multiple nodes is done via separate TCP/IP links.
The DSSI storage subsystem is functionally emulated and operates at a much higher throughput than the original hardware. Connection to physical DSSI hardware is neither possible nor planned for future releases.
The current version of DSSI emulation for CHARON-VAX supports up to 3 VAX nodes in a virtual DSSI cluster and handles a maximum cluster size of 8 nodes. A single virtual DSSI network supports up to 256 storage elements.
For more details on DSSI configuration follow this link.
Configuration steps
To create a CHARON-VAX DSSI cluster, two elements must be configured:
"SHAC" host adapter
"HSD50" storage controller
It is advisable to start any field test based on the cluster examples provided below
DSSI hardware topology is emulated by establishing TCP/IP channels between the emulated SHAC host adapters of each CHARON-VAX system. The emulated HSD50 storage controllers are then connected to every SHAC host adapter in the virtual DSSI network.
Cluster operation requires (virtual) disks that are simultaneously accessible by all CHARON-VAX nodes involved. This can be implemented for instance by using a properly configured iSCSI initiator / target structure or a fiber channel storage back-end. Disks on a multiport SCSI switch are not acceptable, as a SCSI switch does not provides true simultaneous access to multiple nodes.
It is advisable to start any field test with implementing the cluster examples provided below
Example 1: Dual node DSSI cluster with 4 shared disks
To setup two emulated VAX 4000 Model 108 nodes, we need two host machines, preferably running the same version of Linux.
Assume that these host systems have network host names CASTOR and POLLUX in the host TCP/IP network.
The following are CHARON-VAX configuration files for the emulated VAX 4000 Model 108 nodes running on CASTOR and POLLUX:
| CASTOR node |
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| POLLUX node |
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Let's review both configurations step-by-step.
The first line of both configuration files establishes parameters for the preloaded "PAA" SHAC host adapter. Only 2 parameters of SHAC are important for us in this situation:
Parameter Description port An integer value that specifies the TCP/IP port number on which an emulated SHAC host adapter listens for connections from another emulated SHAC host adapter.
Possible port values are from 1024 through 32767.
host A string value that specifies the TCP/IP host name (and optionally TCP/IP port number) to connect to another emulated SHAC host adapter.
The syntax for the string is “host-name[:port-no]”, with possible values for "port-no" in the range from 1024 through 32767.
Thus, CASTOR connects to POLLUX's port 11021 and listens for POLLUX's connection on port 11012, POLLUX connects to CASTOR's port 11012 and listens for CASTOR's connection on port 11021
Second and third lines of both configuration files are for loading "DISKS" HSD50 storage controller and its parametrization:
Parameter Description dssi_host A string value that specifies an instance name of the emulated SHAC host adapter serving virtual DSSI network.
If this value is not set, CHARON-VAX tries to locate the host adapter automatically. This automatic lookup works only if the CHARON-VAX configuration has exactly one instance of emulated SHAC host adapter.
dssi_node_id An integer value that specifies address of emulated HSD50 storage controller on virtual DSSI network. Possible values are from 0 through 7 (initially set to 0).
scs_system_id A string value that specifies SCSNODENAME of emulated HSD50 storage controller.
The string is up to 10 characters long. Possible characters are uppercase letters A through Z , figures 0 through 9.
mscp_allocation_class An integer value that specifies ALLOCLASS of emulated HSD50 storage controller.
Possible values are from 0 through 255 (initially set to 0).
In both configuration files, the data related to the emulated HSD50 storage controller "DISKS" must be identical. Not following this rule can cause data corruption on the (virtual) disks.
- The next lines demonstrate mapping "DISKS" HSD50 storage controller to disk images, shared between both hosts.. A "container" parameter is used for this purpose. This example assumes that all disk images are accessible from both host machines via network share (NFS, SAMBA) or some other realization.
Example 2: Triple node DSSI cluster with multiple iSCSI disks
In this example we assume that all three host systems have a iSCSI initiator and are connected to a common iSCSI server. The iSCSI disk server provides 8 virtual disks with R/W access on all hosts. These disks are configured as "/dev/sdc0" ... "/dev/sdc7" on each of the host machines.
Since the storage configuration must be identical on all three nodes, it is recommended to describe the storage structure in a separate configuration file (to be included in each CHARON-VAX configuration file with "include" instruction and name of the configuration file "disksets.cfg") and store it on a common network share ("/mnt/share") (NFS, SAMBA, etc):
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CHARON-VAX configuration file for the emulated VAX 4000 Model 108 node running on HOST001 is as follows:
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CHARON-VAX configuration file for the emulated VAX 4000 Model 108 node running on HOST002 is as follows:
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CHARON-VAX configuration file for the emulated VAX 4000 Model 108 node running on HOST003 is as follows:
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