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Degraded appliance operating modes, such as a cluster takeover in what is designed to be an
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active-active cluster configuration
While the possibility of queue overruns is remote, it can be eliminated entirely if one is willing
to limit queue depth on a per-client basis. To determine a suitable queue depth limit, one should
take the number of target ports multiplied by the maximum concurrent commands per port
(2048) and divide the product by the number of LUNs provisioned. To accommodate degraded
operating modes, one should sum the number of LUNs across cluster peers to determine the
number of LUNs, but take as the number of target ports the minimum of the two cluster peers.
For example, in an active-active 7420 dual-headed cluster with one head having 2 FC ports and
100 LUNs and the other head having 4 FC ports and 28 LUNs, one should take the pessimal
maximum queue depth to be two ports times 2048 commands divided by 100 LUNs plus 28
LUNs -- or 32 commands per LUN.
Tuning the maximum queue depth is initiator specific, but on Solaris, this is achieved by
adjusting the global variable ssd_max_throttle.
To troubleshoot link-level issues such as broken optics or a poorly seated cable, look at the error
statistics for each FC port. If any number is either significantly non-zero or increasing, that
may be an indicator that link-level issues have been encountered, and that link-level diagnostics
should be performed.
Related Topics
Configuring FC Port Modes (BUI)
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Discovering FC Ports (BUI)
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Creating FC Initiator Groups (BUI)
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Associating a LUN with an FC Initiator Group (BUI)
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Changing FC Port Modes (CLI)
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Discovering FC Ports (CLI)
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Creating FC Initiator Groups (CLI)
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Associating a LUN with an FC Initiator Group (CLI)
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Scripting Aliases for Initiators and Initiator Groups (CLI)
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Configuring SAN iSCSI Initiators
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Creating an Analytics Worksheet (BUI)
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Adding an iSCSI Target with an Auto-generated IQN (CLI)
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Adding an iSCSI Target with a Specific IQN and RADIUS Authentication (CLI)
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Adding an iSCSI Initiator with CHAP Authentication (CLI)
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Adding an iSCSI Target Group (CLI)
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Adding an iSCSI Initiator Group (CLI)
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Configuring SRP Target (BUI)
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Configuring SRP Targets (CLI)
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Configuring SRP Targets (CLI)
Configuring the Appliance
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