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SentinelRAID 170 Installation and Hardware Reference Manual
4-4 SR 170 Topologies
4.2.2 Dual Host Connection
In Figure 4-2 two channels (CH0 and CH1) are configured as host channels and two
channels (CH2 and CH3) are configured as drive channels. The firmware (FW) can be
used to create LDs. These LDs must in turn be mapped to the host channels.
Figure 4-2: Dual Host Connection
♦ Creating redundant host paths: If access to data is a critical requirement,
redundant data paths to different LDs or logical volumes (LVs) can be created. To
do this, logical units (LDs or LVs) are mapped to both the host channels (CH0 and
CH1 in Figure 4-2). This will ensure that if one host computer fails, the second
host computer will be able to access the logical units on that host computer.
NOTE: To create dual-redundant data paths on the host side, it is necessary for
third-party failover software to be installed on the host computer(s).
♦ Physically isolating one OS system from another: The multiple-host configuration
can also be applied when the array is shared by two or more systems. Using each
host channel for a host adapter on different host computers can physically isolate
one OS system from another.
This configuration is applied when two systems cannot share the same SCSI bus as
the access route to storage. Unless some file system "lock manager" is available,
physical drives should be configured into different logical drives or logical
volumes, and each logical unit should be mapped to IDs/LUNs on each host
channel. In this way, each host computer will be accessing separate logical units.