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Globus Toolkit on HP TruCluster systems

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Alpha TruCluster overview

Unlike other clustering solutions, each node of a TruCluster has an externally addressable name, making it possible to treat each node as a stand-alone Grid endpoint. Alternatively, one can access a TruCluster node by using its cluster alias, in which case the job is submitted to any one of the cluster nodes. Unfortunately, due to the fact that GSI only supports a single host name per certificate per server, the Grid administrator must choose between these two configurations. Before discussing the pros and cons of each approach, we must first understand CDSLs.

CDSLs and Globus installations

Tru64 UNIX employs Context Dependent Symbolic Links (CDSLs) which allow for run-time interpolation of symbolic links based on the cluster node name. For example, a symlink that points to "/tmp/{member}/abc" resolves to "/tmp/fred/abc" on node "fred" and "/tmp/barney/abc" on node "barney". CDSLs can be used to simplify the installation of Globus regardless of which method is selected.

Unfortunately, Globus does not easily lend itself to installation in a common, shared directory. While some directories (e.g., "$GLOBUS_LOCATION/var") can be made a CDSL, only a subset of the files and directories under "$GLOBUS_LOCATION/etc" are common across an installation.

Node-specific installation

The advantages and disadvantages of a Node-specific Installation are as follows:
  • + A client may select a specific node for job submission.
  • + MDS may be configured to run on every node.
  • - Each node requires unique certificates.
  • - Each node must be installed to a separate location.
  • - No failover for Gatekeeper and GridFTP services.

Before installing Globus on any cluster node, create a CDSL for the "/etc/grid-security" directory as well as one for Globus installation directory (i.e., identified by $GLOBUS_LOCATION). This procedure must be done once, as the superuser, on any cluster node. An example command sequence (where the $GLOBUS_LOCATION variable is installation-dependent) follows:

    $ GLOBUS_LOCATION=/opt/globus/nodespec
    $ mkdir -m 755 -p /etc/grid-security ${GLOBUS_LOCATION}
    $ mkcdsl -a /etc/grid-security
    $ mkcdsl -a ${GLOBUS_LOCATION}

Additionally, when registering an installation through the GTbuild script, the registration directory itself should also be a CDSL. This procedure must be done once, as the superuser, on any cluster node. An example command sequence (where the $GTKREG_DIR variable is installation-dependent) follows:

    $ GTKREG_DIR=/globus
    $ mkdir -m 755 -p ${GTKREG_DIR}
    $ mkcdsl -a ${GTKREG_DIR}

Follow the instructions for a Globus on Multi-homed host installation on every node of the cluster, Note that, since "/etc/inetd.conf" is a shared file, it is only necessary to modify it on one cluster node. However, after making the change, the inetd server must be restarted on every node:

    $ nodes=`clu_get_info -raw | grep '^M.*:UP:' | \
           awk -F: '{ print $3 }'`
    $ for mem in $nodes; do
    >   rsh $mem '/usr/sbin/inetd -h'
    > done

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Cluster-wide installation

The advantages and disadvantages to doing a Cluster-wide Installation are:
  • + Single shared Globus installation and certificates.
  • + Automatic fail-over for Gatekeeper and GridFTP services.
  • - Can not select a specific node for job submission.
  • - MDS becomes much more complex (see "MDS " below).

Use the cluster alias for the GCHN and follow the instructions for installing Globus on Multi-homed hosts (i.e., the $GLOBUS_HOSTNAME variable and all certificate requests should use the cluster alias). Next, do the following:

  • Edit the "/etc/clua_services" file and add these lines:
        gsigatekeeper   2119/tcp        in_multi,out_alias,static
        gsiftp          2811/tcp        in_multi,out_alias,static
    
    The "in_multi" option allows incoming connections to be handled by any cluster node. The "out_alias" option will ensure that the outgoing IP address is that of the cluster alias (since this is the host name used in the certificate subject) and "static" ensures that the port will not be dynamically assigned.
  • On each cluster node, reload the "/etc/clua_services" file ("/usr/sbin/cluamgr -f") and restart the inetd server ("/usr/sbin/inetd -h"). This procedure must be done once, as the superuser, on any cluster node. An example command sequence follows:
        $ nodes=`clu_get_info -raw | grep '^M.*:UP:' | awk -F: '{ print $3 }'`
        $ for mem in $nodes; do
        >   rsh $mem '/usr/sbin/cluamgr -f; sleep 1; /usr/sbin/inetd -h'
        > done
    
    
  • Instruct everyone to use the cluster alias to communicate with the Cluster.

As mentioned above, one disadvantage to the Cluster-wide Installation is that there is no way to directly submit a job to a specific node. One could use a job manager (e.g., OpenPBS or LSF) to steer an application, or alternatively, the Globus fork job manager could be coerced into running a job on a specific node by vectoring the submission through the rsh(1) command.

MDS issues

There is no ideal solution for running the MDS provider on a system set up using the Cluster-wide Installation method. By default, MDS runs on a single node and only reports node-specific information. Running MDS on only one node makes information such as available memory and CPU data all but useless. One could run MDS on each node (as is done for a Node-specific Installation), however authentication either will not work (if the LDAP certificates use the GCHN), or individual LDAP certificates would need to be installed on each node. In the latter case, "/etc/grid-security/ldap" would become a CDSL and clients -- who normally use the GCHN -- would have to query each node individually (querying against the GCHN is pointless as that would only return MDS data for one random node).

Employing a GIIS on one node to collect information from each individual MDS GRIS provider is one solution to this problem. Another is to set up Ganglia to collect data from all nodes of the cluster and feed it back to a GIIS.


Prerequisite applications

Since Truclusters run Tru64 Unix, when building GT2 or the Pre-WS (pre-web services) GT4 packages, the existing GT2 Tru64 Unix prerequisites must be satisfied. If installing GT4, these GT platform notes for HP systems are applicable.

Other TruCluster notes

If Globus was installed on a shared disk, the post-install procedure for the setup-globus-gram-job-manager script will display messages of the form:
    Creating state file directory.
    WARNING: It looks like [...]/tmp may not be on a local filesystem.
    WARNING: The test for local file systems is not 100% reliable.
             Ignore the below if this is a false positive.
    WARNING: The jobmanager requires state dir to be on a local filesystem
    WARNING: Rerun the jobmanager setup script with
             the -state-dir= option.

This message can be ignored unless the installation directory is actually being shared with other nodes. If this is the case, follow the instructions above for configuring Globus directories using CDSLs and then run the following command to reconfigure the GRAM job manager:
    $ ${GLOBUS_LOCATION}/setup/globus/setup-globus-gram-job-manager --state-dir=${GLOBUS_LOCATION}/tmp
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