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

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Message-ID: <4FC54D62.3080003@ddn.com>
Date:	Tue, 29 May 2012 18:27:46 -0400
From:	Karandeep Chahal <kchahal@....com>
To:	Michael Reed <mdr@....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.

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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