Troubleshooting guide

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Cisco Wide Area Application Services Configuration Guide

OL-26579-01

Chapter 1 Planning Your WAAS Network

Calculating the Number of WAAS Devices Needed

When the threshold value of an operational system aspect is exceeded, Cisco WAAS may not meet its

expected service level. This situation might result in degraded performance.

The source of the limitation might originate from a specific Cisco WAAS device (WAAS

Central Manager, branch WAE, or data center WAE), the entire Cisco WAAS system, a hardware

constraint, or the network connecting the distributed software entities. In some cases, the limitation

might be resolved by adding more resources or by upgrading the hardware or software.

When planning your network, consider the operational capacity, such as the number of users it should

support, how many files it should support, and how much data it should cache.

When planning your WAAS network, refer to the following additional guidelines:

• Number of WAAS Central Managers— All networks must have at least one WAAS Central

Manager. For larger networks, you should consider deploying two WAAS Central Managers for

active and standby back-up, high availability, and failover. A WAAS Central Manager is deployed

on a dedicated appliance.

• Number of WAEs—A minimum of two WAEs are required for traffic optimization; one WAE is

required on either side of a network link (for example, one in the branch office and one in the data

center). A single site can have more than one WAE for redundancy purposes.

• Number of branch WAEs—At least one branch WAE is required in each remote office. Larger offices

usually have multiple departments whose users work with different servers in the central office. In

this situation, you can manage your system easier by following the organizational structure with a

branch WAE for each department. In certain situations, multiple branch WAEs can be clustered and

configured using WCCP to provide failover capabilities. WCCP is the recommended method for

larger user populations.

• Number of data center WAEs—Each organization must have at least one data center WAE.

• Number of ANCs—If you are using the AppNav deployment model, at least one ANC is required.

When determining the number of the component types required by your organization, consider the

following factors:

• Number of users connecting to the system—This number depends on the static and dynamic

capacities defined for the system:

–

Static capacities—Defines the number of user sessions that can connect to the system before it

reaches its capacity.

–

Dynamic capacities—Defines the amount of traffic handled by the servers, which means the

amount of work being performed on the network. For example, consider whether the users

currently connected to the system place a heavy or light load on it.

Note You should calculate dynamic limits based on the specific load assumptions that are particular

to each customer.

• Total number of users in all branches that connect to the file servers through the data center WAE—

When the number of users is more than one data center WAE can support, you must add one or more

additional data center WAEs to the network.