3.7.0 HP StorageWorks HP Scalable NAS File Serving Software administration guide - HP Scalable NAS 3.7 for Linux (AG513-96002, October 2009)

The sentinel node
The nodes on the source cluster that are involved with replication are called the
replication group. One node from the replication group coordinates replication
activities such as performing the file transfers. This node is called the sentinel node.
When you configure replication, you can specify the node that you prefer to use as
the sentinel.
Occasionally when the replication group is formed and replication starts, a different
node may actually become the sentinel node. This can happen for a variety of reasons;
for example, the preferred node may have been down at the time the replication
group was formed. You can use replication commands to determine which node is
currently acting as the sentinel node and to force the preferred sentinel to become
the actual sentinel node.
Cluster requirements
The source and destination clusters must both be running the same operating system
and HP Scalable NAS 3.7.0 (or higher). The source cluster must be able to reach
the destination cluster via ssh.
Change required for SLES10
The LSB package provided with the SLES10 operating system must be removed before
using replication. This package conflicts with replication operations and causes
replication to fail. Use the following command to remove the package:
rpm -e lsb
Replication tuning
Replication substantially increases the work load for the system that is the replication
source; not only does it have to create the data to be replicated, that data must be
noted as needing to be replicated, and the system must read the data to be replicated
from disk and transmit it to the destination cluster. This places a higher load on the
systems participating in replication, especially the sentinel node, which is responsible
for sending all of the filesystem changes for all nodes to the destination cluster. For
best performance and to ensure the best possible replication success, systems must
be tuned for replication.
Replication impacts the system most heavily in the following areas:
Configure and manage replication250