Benefits of stacking appliances

Stacking gives you the ability to scale storage and expand retention time for capture data.

While the stack is actively capturing data, you can complete the following actions:
  • Take an individual Stack Node offline, upgrade it, and reinsert it back into the stack.
    Note: This capability does not apply to the Stack Controller.
  • Add an appliance to expand the capacity of a stack.

    The appliance hardware and storage size can vary. All available storage in the stack is used for data capture.

Data storage

The ring topology of the stack helps to protect the capture data. The capture data is stored in the stack by time frame; that is, an appliance holds all capture data for a certain time frame and overwrites the oldest data.

The time frame for the entire stack is established by concatenating all appliances in order. For example, in a stack with three appliances, Appliance A stores data from time frame 0-9, Appliance B stores data from time frame 10-19, and Appliance C stores data from time frame 20-29. As the appliances fill up with data, the oldest capture data is overwritten first. Appliance A now stores data from time frame 30 -39, overwriting data from time frame 0-9.

If an appliance goes offline, a gap in the capture data occurs, but the gap is limited to the time frame of the data that is held on the offline appliance. In the stack example, if Appliance B is offline, data from time frame 10-19 is not available, but all other capture data in the stack is available.