EonStor DS S48 Series Hardware Manual
3.1.3
Maximum Concurrent Host LUN Connection (“Nexus” in SCSI)
The "Max Number of Concurrent Host-LUN Connection" menu option is used to set
the maximum number of concurrent host-LUN connections. Change this menu option
setting only if you have more than four logical drives or partitions. Increasing this
number might increase your performance.
Maximum concurrent host LUN connection (nexus in SCSI) is the arrangement of the
controller internal resources for use with a number of the current host nexus.
For example, you can 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 all queued in the cache and are called four nexus.
If there is I/O in the cache with four different nexus, and another host I/O comes with
a nexus different than the four in the cache (for example, host A accesses ID 3), the
controller returns busy. This occurs 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.
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