# Performance Impact and Scalability Considerations

Some performance impact occurs when a new secondary line module is provisioned or inserted, with the primary module containing the maximum number of tunneled PPP sessions. The synchronization of data occupies some backplane bandwidth, which might slightly impact the call setup rate during the time the secondary module is plugged in to the slot.

The maximum number of ingress or egress policy statistic entries that can be configured is 512,000 entries. Each statistic entry is a combination of an 8-byte packet counter and an 8-byte octet counter. The configuration of this maximum number of policy statistics causes the collection of 8 MB of data (512,000 entries * 16 bytes = 8,192,000 bytes).

| Tip: Because the collection of statistics and mirroring of data is processor-intensive, we recommend that you do not exceed 2 MB of statistics data when you configure stateful line module switchover. The preservation of 2 MB of statistical information maps to an average of 8 statistics entries per subscriber for a fully scaled subscriber environment (16,000 subscribers * 8 statistics per subscriber * 16 bytes per entry = 2,048,000 bytes). You can maintain the limit on 2MB of statistics by reducing the number of subscribers and increasing the statistics per subscriber, or by increasing the number of subscribers and reducing the statistics per subscriber.

Although the applications that support stateful line module switchover are enhanced in their infrastructure and design capabilities, performance of the line modules is not impacted by the improvements made to the compatible protocols and applications. In a scaled topology, simultaneous switchover of all the line modules in a chassis is supported. The operations of line modules that no not support stateful switchover is also not impacted in any manner, owing to the changes made to HA-safe applications.

#### Related Documentation

- Application Support for Stateful Line Module Switchover
- System Operations When Stateful Line Module Switchover Is Enabled