TS/MP Release Supplement

ACS Subsystem
HP NonStop TS/MP Release Supplement—546055-006
1-20
Load Balancing PATHMON Link Requests in a
Pathway Domain
the distribution of link requests across PATHMONs is in line with the weights assigned
to the PATHMONs. At low load levels, the link usage algorithm favors links that are
more responsive. Requests are processed using the released links rather than
requesting a new link. As a result, the load distribution of the links might appear
uneven at low load levels, but this does not adversely affect the response time.
The PATHMON weights in the ACSCTL file must match the server process
configuration (as indicated by the MAXSERVERS parameter) of the individual Pathway
environments that form the respective domains. Under load conditions, the ACS
subsystem tries to get links proportionate to the configured weight. If a PATHMON with
a higher weight in the ACSCTL file has few server processes configured, it will not be
able to serve all the link requests received, thereby resulting in load imbalance.
Example:
Consider that the ACSCTL file on system \A has the following weights defined for
domain %DOM.
%DOM = \A.$PM1:50, \A.$PM2:10, \A.$PM3:40
The PATHMONs $PM1, $PM2, and $PM3 have servers SERVER-CORRECT and
SERVER-WRONG configured. The LINKDEPTH and MAXLINKS parameter values are
set to 1 for both the servers in all the PATHMONs. The MAXSERVERS parameter
values for the servers are:
The above configuration shows the following:
•
The SERVER-CORRECT server has 50, 10, and 40 percent of processes
configured in
$PM1, $PM2, and $PM3 respectively. This is how the weights
have been defined for PATHMONs
$PM1, $PM2, and $PM3 for the domain
%DOM in the ACSCTL file. Under load conditions, when most links must be
utilized, SERVER-CORRECT will achieve proper load balance against the
configured PATHMON weights.
•
The SERVER-WRONG server has 10, 50, and 40 percent of processes
configured in
$PM1, $PM2, and $PM3 respectively. During load conditions, the
ACS subsystem will try to get maximum links from
$PM1. Because the number
of server processes configured is not sufficient, the links will be acquired from
other PATHMONs. This results in an imbalance as compared to the configured
PATHMON weights.
Using too many dynamic server processes can distort the distribution of server links.
Using the dynamic links to service new Pathsend requests might result in an uneven
link distribution, as measured against the defined PATHMON weights.
Example:
PATHMON Names $PM1 $PM2 $PM3
Server Names
SERVER-CORRECT 10 2 8
SERVER-WRONG 2 10 8