6.7

Table Of Contents
Figure 182. Host-Based Path Failover
IP network
hardware
iSCSI
host 1
SP
iSCSI storage
HBA2 HBA1
software
iSCSI
host 2
NIC2 NIC1
software
adapter
Hardware iSCSI and Failover
With hardware iSCSI, the host typically has two or more hardware iSCSI adapters. The host uses the
adapters to reach the storage system through one or more switches. Alternatively, the setup might include
one adapter and two storage processors, so that the adapter can use different paths to reach the storage
system.
On the illustration, Host1 has two hardware iSCSI adapters, HBA1 and HBA2, that provide two physical
paths to the storage system. Multipathing plug-ins on your host, whether the VMkernel NMP or any third-
party MPPs, have access to the paths by default. The plug-ins can monitor health of each physical path.
If, for example, HBA1 or the link between HBA1 and the network fails, the multipathing plug-ins can
switch the path over to HBA2.
Software iSCSI and Failover
With software iSCSI, as shown on Host 2 of the illustration, you can use multiple NICs that provide
failover and load balancing capabilities for iSCSI connections.
Multipathing plug-ins do not have direct access to physical NICs on your host. As a result, for this setup,
you first must connect each physical NIC to a separate VMkernel port. You then associate all VMkernel
ports with the software iSCSI initiator using a port binding technique. Each VMkernel port connected to a
separate NIC becomes a different path that the iSCSI storage stack and its storage-aware multipathing
plug-ins can use.
For information about configuring multipathing for software iSCSI, see Setting Up Network for iSCSI and
iSER.
vSphere Storage
VMware, Inc. 204