Juniper Networks E-Series - Manual (Page 39)

Redundancy Features
E-Series Routers
1-17
primary SRP module will hereafter be referred to as the primary NVS
card.)
If the capacity of the primary NVS card is equal to or smaller than that of
the redundant NVS card, the system copies all the files from the primary
NVS card to the redundant NVS card. However, if the capacity of the
primary NVS card exceeds that of the redundant NVS card, the system
creates an invisible synchronization reserve file on the primary NVS
card, provided that there is enough space for the file.
The purpose of the synchronization file is to prevent the creation of data
that will not fit on the redundant NVS card. The file contains no useful
data, and is not visible when you view the files in NVS. The size of the file
is equal to the difference in capacities of the two NVS cards. For example,
if the primary NVS card has a capacity of 224 MB and the redundant
NVS card has a capacity of 220 MB, the size of the synchronization file is
4 MB, and only 220 MB of space is available on the primary NVS card.
If there is not enough space on the primary NVS card to create the
synchronization reserve file, the
synchronize command fails, and a
warning message is displayed on the console. To resolve this issue, either
delete unwanted files from the primary NVS card or replace the
redundant NVS card with a higher-capacity NVS card.
Line Modules
Note: This section applies to ERX-7xx/14xx models only. ERX-310 routers do not
offer line module redundancy.
ERX-7xx/14xx models support line module redundancy for several line
modules. For details about which line modules support redundancy, see
Chapter 12, Module Specifications . In this scheme, an extra line module
in a group of identical line modules provides redundancy in case of line
module failure. To use this feature, you need a:
• Spare line module
• Redundancy midplane
• Redundancy I/O module
A redundancy midplane may cover 3–6 slots. It provides additional
connectivity that enables the spare line module to assume control of the
I/O module associated with any failed line module in the redundancy
group. The spare I/O module provides connectivity from the spare line
module to the redundancy midplane.