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Chapter 2: Hardware installation
Configuring the host-side parameters
For the host-side parameters, we strongly recommend that you use the default settings of your system.
If you need to adjust the host-side parameters, consult your on-site technical personnel or seek
technical support from your vendor.
Familiarizing the Maximum Concurrent Host LUN Connection (Nexus in SCSI)
The menu option
Max Number of Concurrent Host-LUN Connection
allows you to set the maximum
number of concurrent host LUN connections. This is the arrangement of the controller internal resources
to use with a number of current host nexus.
For example, if you have 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 queued in the cache, which are called four nexus. If there is an I/O in the cache
with these four nexus and another host I/O comes with a nexus different from the four in the cache (e.g.
host A accesses ID 3), the controller returns as busy. This happens with the concurrent active nexus. If
the cache is cleared, it accepts four different nexus again. Many I/O operations can be accessed via the
same nexus.
Knowing the Maximum Queued I/O Count
The menu option
Maximum Queued I/O Count
allows you to configure the maximum number of I/O
operations per host channel that can be accepted from the servers. The predefined range is from
1 to 1024 I/O operations per host channel. You can also choose
Auto
, which sets the automatic
configuration. The default value is 256 I/O operations.
The appropriate setting for this option depends on how many I/O operations the attached servers are
performing. This varies according to the amount of the host memory present as well as the number of
drives and their respective sizes. Usually, the optimum performance occurs from using
Auto
or
256
settings.
For more information, refer to the firmware manual that came with your system.
