Juniper Networks ERX-1410 - Manual (Page 32)

CHAPTER 1
ERX System Overview 1-12
SRP I/O module located in the rear of the chassis. If the primary SRP
fails, the redundant SRP module assumes control without rebooting or
initializing itself. (As a consequence, if you upgrade software, you must
copy the software to the redundant SRP and reboot it.) For information
about configuring and managing SRP module redundancy, see
ERX
System Basics Configuration Guide, Chapter 5, Managing Line Modules
and SRP Modules
.
After you install two SRP modules, the modules negotiate for the primary
role. A number of factors determine which module becomes the primary;
however, preference is given to the module in the lower-numbered slot.
The SRP modules record their latest roles and retain them the next time
you switch on the system. For information about installing SRP modules,
see
Chapter 3, Installing ERX Modules .
NVS Cards
If you have two SRP modules installed in a system, you can use NVS
cards of different capacities on the SRP modules. The effective capacity
of the higher-capacity NVS card will equal that of the lower-capacity
NVS card. For information about installing NVS cards, see
Chapter 3,
Installing ERX Modules .
When you install new NVS cards or SRP modules, you must issue the
synchronize command to match the file system of the NVS card on the
redundant SRP module with the file system of the NVS card on the
primary SRP module. (The NVS card on the redundant SRP module will
hereafter be referred to as the redundant NVS card; the NVS card on the
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.