I'm currently testing replication of IBM SVC with Cisco 9222i switches. This is using the Global (asynchronous) mirror option. Both Production and DR storage is at the Production site at present
When I throttle the bandwidth with the tcp-max-bandwidth on the "Production" side we start to get I/O latency on the hosts attaching to the SVC. When we throttle bandwidth at the "DR" side we don't notice a problem.
As this is asynchronous replication the hosts shouldn't be getting I/O latency so the only thing I can think is that when I/O is backing up on the 9222i for transmission it is chewing up switch resources which is slowing the servers access to storage.
We seem to have narrowed down the problem. Their is a Brocade switch in the environment and when we disable the ISL to this switch it seems to negate the problem. One of the other issues we have is that servers plugging into the Brocade have their port disabled when they login to the switch. This problem disappears when we drop the FCIP link to the other site.
So it looks like there is an interoperability issue. IBM are looking into it.
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