According to the documention
it must be possible overriding jboss.server.log.dir and jboss.server.data.dir.
"Users can add their own paths or override all except the first five of the above by adding a path element to their configuration file."
When using something like
<paths>
<path name="jboss.server.log.dir" path="log/cluster-server1" relative-to="jboss.server.base.dir"/>
<path name="jboss.server.data.dir" path="data/cluster-server1" relative-to="jboss.server.base.dir"/>
</paths>
in the standalone.xml, an error is thrown during start-up, saying that jboss.server.log.dir is reserved.
By using system properties like
<system-properties>
<property name="jboss.server.log.dir" value="/some/path"/>
</system-properties>
you get the clear message that the property jboss.server.log.dir must be set on the command-line (otherwise it is too late).
When setting the properties on the command-line
${JBOSS_HOME}/bin/standalone.sh --server-config=cluster-server1.xml -Djboss.server.log.dir=${JBOSS_HOME}/standalone/log/cluster-server1 -Djboss.server.data.dir=${JBOSS_HOME}/standalone/data/cluster-server1
there is no problem.
Is the last option the only way? If so it might be handy to update the documentation.
I suppose it is the only option to use the "-D" parameter to change it.
I've checked for domain mode where it is also not possible to change it per server.
I've opened a documentation bug for this.