HP StorageWorks Enterprise File Services WAN Accelerator 3.0.4 deployment guide (AG421-96001, March 2007)

HP STORAGEWORKS ENTERPRISE FILE SERVICES WAN ACCELERATOR DEPLOYMENT GUIDE 17
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 executed by HP EFS WAN Accelerators ahead of the client
only 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.
 Server Locations. A central server location that remote offices access data
from. Typically, a server location is a data center serving branch offices or
regional offices that access data that is centrally located.