linux-kernel - Re: [PATCH 1/1] ib_srp: Infiniband srp fast failover patch.

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Message-ID: <4FC55351.6020503@sgi.com>
Date:	Tue, 29 May 2012 15:53:05 -0700
From:	Michael Reed <mdr@....com>
To:	Karandeep Chahal <kchahal@....com>
CC:	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dillowda@...l.gov" <dillowda@...l.gov>,
	"roland@...nel.org" <roland@...nel.org>,
	"sean.hefty@...el.com" <sean.hefty@...el.com>
Subject: Re: [PATCH 1/1] ib_srp: Infiniband srp fast failover patch.

Thank you for clarifying!

On 05/29/2012 03:27 PM, Karandeep Chahal wrote:
> Hi Michael,
>
> Yes, I tried reconnecting the targets and removing reinserting ib-srp.
>
> Thanks
> Karan
>
>
> On 05/29/2012 05:51 PM, Michael Reed wrote:
>> Did you subsequently reconnect the target and confirm appropriate behavior?
>>
>>
>> On 05/29/2012 02:07 PM, Karandeep Chahal wrote:
>>> Subject: [PATCH] Infiniband srp fast failover patch. Currently ib_srp does
>>>      not do anything on receiving a DREQ from the target, it
>>>      only sends a response back. Further it also does not
>>>      monitor port (down) events. I have patched srp to remove
>>>      scsi devices when a port down event is received or if the
>>>      target sends a DREQ. Currently even though the target
>>>      notifies the initiator of its intentions of going away, the
>>>      initiator ignores that information. Later the initiator
>>>      gets upset when the devices "suddenly" disappear resulting
>>>      in srp initiating an error recovery process which takes a
>>>      long time. This caused high failover latencies as compared
>>>      to fibre channel. In my experiments with RHEL 6.0 and 6.2 I
>>>      encountered failover time that exceeded 2 minutes and 20
>>>      seconds (despite tweaking /etc/multipath.conf and
>>>      /sys/block/<>/timeout). With this patch the failover takes
>>>      30 seconds. I have tested this patch with and without a
>>>      switch.
>>>
>>> Yours, etc.
>>> Karan
>>>
> --
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