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List:       freebsd-scsi
Subject:    Re: adding a "retry command after a delay" error
From:       Matthew Jacob <mj () feral ! com>
Date:       2010-04-05 20:34:52
Message-ID: 4BBA496C.4040908 () feral ! com
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On 04/04/2010 11:37 PM, Alexander Motin wrote:
> Matthew Jacob wrote:
>    
>> This is something I whipped up for dealing with some
>> active/active-after-failover-time systems. I wanted to have a general
>> facility to say of an ASC/ASCQ- retry the command, but after a period of
>> delay.
>>
>> Wonder if anyone had comments?
>> http://people.freebsd.org/~mjacob/delay_diffs.txt
>>      
> I am not SCSI expert yet, but it seems OK for me. But I see two related
> questions there: delay time and number of retries allowed.
>
> Most of peripheral drivers now AFAIR ask to do only few (2-5) retries,
> so if delay will be short - it may give up too early, but long delay
> will probably reduce performance.
>
>    
I've been doing some rethinking about this. It really is the devq that I 
want to have stopped and retried with a timeout- not the entire sim.

Your point about periph drivers is well taken, and I thought about just 
capturing this one in da, but it turns out that both sg && pass have the 
same issue, hence the notion of generalizing it.

The sim change is working for the Panasas guys right now, but that's 
just a bandaid. I'll think some more about this one.

Thanks for the comments!
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