Fragments

The impact of consolidation on WAN

August 5th, 2008 | by Mitja Robas |

Remember the early data centers that used proprietary protocols and platforms? Since those days, data centers have evolved to a decentralized architecture. But “retro” is in, and data centers are evolving to a centralized architecture again.

Seriously, data centers are being re-centralized to consolidate computing resources (namely, servers). Consolidating data center resources brings the following benefits:

• Server virtualization is possible.
• Performance can be scaled more easily.
• High availability is easier to achieve.
• Operational manageability presents less overhead to administrators.
• Duplication of resources can be eliminated.
• Expenses are reduced.

But consolidation has pitfalls if not addressed correctly, especially for remote users. WAN networks are slower than LAN and lack sufficient bandwidth; remote users soon start to complain about poor performance.

The challenge can be tackled differently.
One way would be to add bandwidth to WAN connections. But this is not a good approach for two reasons. First, WAN bandwidth is much more expensive than LAN bandwidth. Second, adding bandwidth does not solve the delay introduced by the length of the WAN links.

You might think that deploying the QoS policy would do the trick, but QoS effectively limits the available bandwidth to different traffic types. Thus, in congested networks, more delay would be introduced for certain traffic types.

For a better solution, look at the applications that are used over WAN - how these applications behave, and how they can be optimized. Often, these applications use chatty protocols and exchange numerous messages even for a simple operation (CIFS, for example). Many remote users use the same data. After transitional connectivity problems occur, getting back up to full speed takes some time.

The key is to optimize protocol behavior, data access and TCP flow. A consolidation solution should also address the following challenges:

• Accelerating applications (thus mitigating the latency introduced by the WAN).
• Eliminating the sending of repetitive data through the WAN.
• Offloading unnecessary server requests.
• Options to run services (such as the print service) locally, without duplicating servers/resources.

Cisco WAAS (Wide Area Application Services) is a solution that tackles these challenges.