Appendix G High Availability
HPSS Installation Guide September 2002 569
Release 4.5, Revision 2
G.7 Metadata Backup Considerations
Special care should be taken when configuring your HA HPSS system to work with the
sfs_backup_util to keep the source, configuration, and backup (LA and TRB) files stored on the
shareddisks. Otherwise a failover could easily make backup files or the sfs_backup_util program
itself unreachable.
Also, crontab entries related to SFS Backup will require special attention. First, they must be kept
up-to-date and synchronized between both nodes of the cluster. Second, some provision must be
madefor the fact that only one of the nodes will be able to run the SFS Backup utility at any given
time (since it resides on a shared file system).
Keeping the crontabs for both nodes in sync is an AIX administration problem that is beyond the
scope of this manual; however, there is a good method to use in order to address the problem of
certain commands being unavailable on the backup node. Put your normal command in a script
whichwill check for the existence of the executable before running the command, and call the script
from your crontab.
For example, if your crontab entry normally looked like this:
0 * * * * /opt/hpss/tools/sfs/sfs_backup_util/run/run.ksh
Then create the a script stored on the local node (/var/run.ksh) like this:
#!/bin/ksh
# Check for existence of the run.ksh before execution
if [ -a /opt/hpss/tools/sfs/sfs_backup_util/run/run.ksh ]; then
/opt/hpss/tools/sfs/sfs_backup_util/run/run.ksh
fi
And replace your normal crontab entry with a call to the script:
0 * * * * /var/run.ksh
Thiswill ensure that your command gets executed on schedule when it is available, and it will keep
cron from sending you error messages when the command is not available.
Just make sure that you make ALL these changes on BOTH nodes in your cluster.
G.8 Using Secure Shell (ssh)
Normally,HA HPSS requiresthat rsh and rcp commands be available in order to function properly.
However, it is possible to configure it to usessh and scp instead for environments where/.rhost
files pose too much of a security risk.
HACMP itself depends heavily on the use ofrsh, so refer to HACMP documentation for
information on what features might not work as expected.
Most dependencies are for configuration and synchronization, which hopefully will be mostly
finishedat install time. It should not affect the ability of the HA HPSS system to fail over properly.