Advantech ASR-5300I Series, User Manual

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35 ASR-5300I Series Hardware User Manual
Chapter 3
S
ystem
Connection
3.2.1 Host-Side Topologies
The primary concern for configuring host-side topologies is to avoid points of failure.
Therefore, we recommend that the host ports be connected to at least two HBAs.
Applying corresponding host port type switches is also advisable (e.g., use Fibre
switches for Fibre host ports).
3.2.2 Host-Side Parameters
We strongly recommend using the default system settings. Users wanting to adjust
the host-side parameters should consult on-site technical personnel or seek technical
support from the vendor.
3.2.3 Maximum Concurrent Host LUN Connections (Nexus in SCSI)
The "Max Number of Concurrent Host-LUN Connections" menu option allows users
to set the maximum number of concurrent host-LUN connections. The maximum
concurrent host LUN connection (nexus in SCSI) refers to the arrangement of the
controller internal resources for use with a number of current host nexus.
Consider the following example, there are four hosts (A, B, C, and D) and four host
IDs/LUNs (IDs 0, 1, 2, and 3) in a configuration where
 Host A accesses ID 0 (one nexus).
 Host B accesses ID 1 (one nexus).
 Host C accesses ID 2 (one nexus).
 Host D accesses ID 3 (one nexus).
These connections are all queued in the cache and known as four nexus.
If there is I/O to the cache with the four nexus, and another host I/O arrives with a
nexus that differs from the four in the cache (for example, Host A accesses ID 3), the
controller will return a busy message. This occurs with all concurrent active nexus. If
the cache is cleared, four nexus can be accepted again. Many I/O operations can be
accessed via the same nexus.
Note! To manage fault-tolerant data paths and optimize data throughput on
multiple data paths, EonPath multipath software, or utilities such as
Linux Device Mapper, must be employed.