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

HP EFS WAN ACCELERATOR DEPLOYMENT GUIDE 15
1 - DESIGNING AN HP EFS
WAN A
CCELERATOR
Essentially, the TCP payload is increased from its normal 64 kilobytes to an
arbitrarily large amount. Because of this increased payload, a given
application that relies on TCP performance (for example, Hypertext Transfer
Protocol or File Transfer Protocol) takes fewer trips across the WAN to
accomplish the same task. When HP EFS WAN Accelerators are deployed in a
network, many applications run 10 to 100 times faster.
Transaction
Prediction
Latency optimization is delivered through Transaction Prediction (TP). TP
involves an intimate understanding of protocol semantics to reduce the
chattiness that would normally occur over the WAN. By acting on
foreknowledge of specific protocol request-response mechanisms, HP EFS
WAN Accelerators streamline the delivery of data that would normally be
delivered in small increments through large numbers of handshakes and
interactions between the client and server over the WAN. As transactions are
executed between the client and server, the HP EFS WAN Accelerators
intercept each transaction, compare it to the database of past transactions. and
make decisions about the probability of future events.
Based on this model, if an HP EFS WAN Accelerator determines there is a high
likelihood of a future transaction occurring, it performs that transaction rather
than waiting for the response from the server to propagate back to the client
and then back to the server. Dramatic performance improvements result from
the time saved by not waiting for each serial transaction to arrive prior to
making the next request. Instead, the transactions are pipe-lined one right after
the other.
Of course, transactions are only executed by HP EFS WAN Accelerators ahead
of the client when it is safe to do so. To ensure data integrity, HP EFS WAN
Accelerators are designed with knowledge of the underlying protocols (for
example, Common Internet File System (CIFS) oplocks) to know precisely
when, and if, it is safe to do so. Fortunately, a wide range of common
applications have very predictable behaviors and, consequently, TP can
enhance WAN performance significantly. When combined with SDR, TP
improves overall WAN performance up to 100 times.
Design and Deployment Overview
The following section summarizes the factors you need to consider before
deploying the HP EFS WAN Accelerator in your network.
When you deploy the HP EFS WAN Accelerator, you must consider the
following elements for both the client and server-side of your network.
1. Determine what kind of site you have:
 User Locations. A branch office that has users but no servers accessed
by the other sites. Typically, a user location is a branch office at a
remote site that accesses data from a headquarters or data center.