Re: FCIP issues with SAN replication

["Chandler, Mel" <melchandler () firstam com>]

Gerald,

 

We do have window scaling enabled, but it's hard set at 32kb per HP's
recommendations.  I will recommend we "supersize" it when we discuss
this issue again.

 

 

Bill,

 

I'm starting to see the pattern here, I'll recommend to HP we set the
window as large as it'll go.  They're following some chart they have in
the user guide based on CIR and latency, that tells them what window
size and scaling factor to set.  They're magic formula has indicated we
should be using 32kb, but I've performed tests with iperf and seen with
larger windows comes greater data rates.  I suspect this is not the
issue though, as it still fails with high TCP timer expired errors.

 

 

Martin,

 

The near side is 10.244.249.31/32 to the far side is 10.245.249.31/32.
I think IP addressing is fine; otherwise, we would have worse problems
where replication would not even start.

 

We're following HP's recommendations and so far they've wanted to set
the window at 32kb.  I agree with you it should be as large as possible,
but for now, this is HP's show.  I will recommend a larger window next
time we discuss the issue with them.

 

I agree there is a configuration problem or timeout that needs to be
adjusted or possibly a malfunctioning NIC in their FC gateways.

 

 

 

Now the update:

 

I discovered if I disable the FCP decode, Wireshark does decode it
correctly as FCIP.

We applied a QoS config to flag SAN replication traffic as DSCP EF and
have seen consistent ping times of ~36ms between sites and the bandwidth
climb as high as 45Mbps on a 1Gbps link.  They still fail after
replicating for a few hours.  Last time we watched them replicate for 12
hours and then fail.  The TCP timer exceed counter seems to indicate
that is the problem, but I have nothing significant on the wireshark
captures to support this.

HP has decided that the MPX110 on the far side needs to be replaced.
I'll post an update after that's done.

 

 

Mel Chandler

Network Engineering

 

The First American Corporation
421 N. Main St., Santa Ana, CA 92701
Direct: 714.250.8295

 

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