Configuration Limits - Cisco MDS 9000 series Configuration Manual
I/o accelerator
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- Command reference manual (1464 pages) ,
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Configuration Limits
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
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Configuration Limits
Table 3-1
Table 3-1
Configuration
Number of switches in a cluster
Number of Switches in the SAN for FC-Redirect
Number of IOA interfaces in a switch
Number of IOA interfaces in a cluster
Number of hosts per target
Number of flows in a cluster
Number of flows across all clusters
Number of flows per IOA service engine (hard limit)
Number of flows per IOA service engine (soft limit)
Note
When the new flows are load balanced again to the functional IOA interface, the soft limit is enforced
to account for IOA interface failures. If the number of switches in the SAN exceeds the scalability limit,
consider using CFS regions as described in
Cisco MDS 9000 Family I/O Accelerator Configuration Guide
3-10
ISL-1 is connected to module 9 and is limited to VSAN 2000, then all the ELS entries specific to
VSAN 2000 will be on module 9. If ISL-2 is connected to module 2 and is limited to VSAN-3000,
then all the ELS entries specific to targets of VSAN-3000 will be on module 2.
IOA flow takes a few seconds to become active upon certain triggers such as host or target port flaps.
PLOGI from the hosts are buffered until the IOA flow becomes active. Once the IOA flow becomes
active, it sends a RSCN to request the host to PLOGI again. Certain target arrays perform a few
back-to-back PLOGIs prior to the flow becoming active and upon seeing a failure requires a manual
corrective action. To prevent this, IOA flows that have been configured for Write-Acceleration are
set up with a default timeout of 10 seconds after which the flow becomes unaccelerated. This is
useful specifically in cases where IOA is unable to take over the flow prior to the timeout. For
example, linecard reloads where no other IOA interface is available to handle the flow. In certain
target arrays, the 10 second timeout is not sufficient and these arrays may require manual recovery
using the storage management interfaces. One example of such a target array is HDS AMS.
The workaround for such a case would be to set the timeout to 5 seconds using the CLI command
"tune wa-fcr-rule-timeout 5" under the ioa cluster configuration sub-mode. This configuration is
cluster-wide persistent across reboots.
lists the IOA configurations and the corresponding limits.
Cisco I/O Accelerator Configuration Limits
"Using FC-Redirect with CFS Regions" section on page
OL-20708-01, Cisco MDS NX-OS Release 5.0(1a)
Chapter 3
Deployment Considerations
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