HP StorageWorks Enterprise File Services WAN Accelerator Deployment Guide (November 2005)

108 10 - SERIAL CLUSTER AND CASCADE DEPLOYMENTS
Serial Cluster Deployment
You can provide increased optimization by deploying several HP EFS WAN
Accelerators back-to-back in an in-path configuration to create a serial cluster.
Serial clustering operates in a spill-over mode where TCP connections beyond
the capacity limit of one of the HP EFS WAN Accelerators in the cluster are
automatically handled by the next HP EFS WAN Accelerator in a cluster. If
one HP EFS WAN Accelerator fails, the next HP EFS WAN Accelerator
automatically take over.
Figure 10-1. Serial Cluster
In this example, HP EFS WAN Accelerator1, HP EFS WAN Accelerator2, and
HP EFS WAN Accelerator3 are configured so that they do not answer probes
from each other and do not intercept inner connections from each other.
Similarly, HP EFS WAN Accelerator4, HP EFS WAN Accelerator5, and HP
EFS WAN Accelerator6 are configured so that they do not answer probes from
each other and do not intercept inner connections from each other. The HP EFS
WAN Accelerators are configured to perform auto-discovery so that they can
find a peer HP EFS WAN Accelerator that is available and that is on the other
side of the Wide Area Network (WAN).
You specify peering rules that when the HP EFS WAN Accelerator receives an
auto-discovery probe it is passed through, accepted, or processed normally
based on the sender of the probe, the client IP address and subnet, the server
IP address and subnet, or the server port.
In a serial cluster when an HP EFS WAN Accelerator reaches its capacity limit,
it stops intercepting new connections and passes them through to the next HP
EFS WAN Accelerator that will intercept them. This process continues until
there are no more HP EFS WAN Accelerators available in the cluster.
In serial cluster deployments:
 The peering rules table is a ordered list of rules and the first rule that
matches the rule is applied.
 To avoid interceptions on inner connections created by other HP EFS
WAN Accelerators in the same cluster, in-path rules are specified to pass-
through connections originating from those HP EFS WAN Accelerators.