Sun Microsystems Virtual Tape Library - Manual (Page 23)

Key VTL features and options
96267 • G Chapter 1 Introduction: VTL appliances and enterprise data-protection 9
controls NDMP agent software on the filer ( D below). This agent software copies
data from the filer over the SAN to virtual tape volumes ( E ) mounted by the backup
media server ( F ), so no softwre has to be hosted on the VTL appliance.
VTL high‐availability option
In a VTL high‐availability system, intelligent self‐monitoring software, redundant
hardware, and high‐availability LAN and SAN configurations protect both the data
path and your ability to manage storage. To help you to better understand the steps
in the failover configuration process, this section provides a high‐level description of
the three key components of the high‐availability VTL solution:
■
“Server node failover” on page 9
■ “Management path failover” on page 10
■
“Storage path failover” on page 11.
Server node failover
The Sun StorageTek VTL high availability option uses two server nodes, each
configured to monitor its companion. Each member of the pair serves as the primary
server for its own storage clients and as the secondary, standby server for those of its
companion. To protect against server failures, each server sends heartbeat
information to its secondary using a service IP address. If heartbeat information
indicates a fatal error in a companion server’s processes, the healthy server notifies
its companion that it is assuming primary server responsibility for both sets of
clients and initiates failover. If the heartbeat information stops altogether, the
healthy server immediately initiates failover. Finally, if a primary server’s own, self‐
monitoring routines detect a storage device connectivity failure and cannot
determine if the failure is local, the primary reports the failure to its companion via
the heartbeat signal. If the companion, secondary server can access all devices,
physical
tape
library
VTL appliance
NAS filer
media server
Data-mover software on NAS filer copies data over SAN to virtual tapes.
SAN fabric
Ethernet LAN
virtual
tape
library
D
E
F