Dell Brocade 815, Troubleshooting Manual

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Brocade Adapters Troubleshooting Guide 115
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Tuning storage drivers
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Interrupt delay
Default:
-
1125 microseconds on the Brocade 415, 425, 815, 825, and 1860
-
25 microseconds on the Brocade 804, 1007, 1010, 1020, and 1741
Valid Range: 0 through 1125 microseconds
Note that the value of 0 disables the delay timeout interrupt.
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Interrupt latency
Default:
-
225 microseconds on the Brocade 415, 425, 815, 825, and 1860
-
5 microseconds on the Brocade 804, 1007, 1010, 1020, and 1741
Valid Range: 0 through 225 microseconds
Note that the value of 0 disables the latency monitor timeout interrupt.
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Interrupt Coalescing
When this feature is turned off, I/O completion requests are not coalesced by the firmware.
While this helps reduce I/O latency, the host CPU will frequently be interrupted, leading to a
slower system response under heavy I/O load (more than 7000 I/Os per second).
When this feature is turned on, the adapter will not interrupt the host until Interrupt delay
duration. Interrupt delay, together with Interrupt latency, helps to reduce the number of
interrupts that the host CPU processes per second, leading to improved overall CPU utilization.
However, if the number of interrupts handled between the Interrupt delay period is relatively
smaller, then this will result in performance degradation as the I/O completion process has
slowed down.
The BCU vhba command can be used to configure these interrupt attributes for the desired
port.
vhba --intr pcifn <-c> {on | off} [<Latency> <Delay>]
Message signaled interrupts (MSI-X)
All Brocade adapters support MSI-X, an eXtended version of the MSI defined in PCI 3.0
specification. MSI-X helps improve overall system performance by contributing to lower interrupt
latency and improved host CPU utilization.
MSI-X is supported in Windows Vista and Windows Server 2008.
To enable MSI-X, set the following registry key value to 0.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\bfad\Parameters\Device\msix_
disable
OS tunable parameters
Please see the section “Storage Stack Drivers” in Disk Subsystem Performance Analysis for
Windows Server 2003 optimizations located on the following website.
http://download.microsoft.com
Please see the sections “Performance Tuning for Storage Subsystem” and “I/O Priorities” in
Performance Tuning Guidelines for Windows Server 2008 located on the following website.
http://www.microsoft.com