Re: ggaoed and ro filesystem during heavy write

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The current version does use the response (since it's a real response) to update the round trip time statistics.  It doesn't use it to complete an I/O request from the block layer.

It also decrements the "lost" counter associated with the remote MAC address when an unexpected response is received, because it was incremented when we decided to retransmit, based on the assumption that the packet was lost, and the unexpected response invalidates that assumption.

The aoe driver routinely issues AoE Query Config broadcasts, so that new targets that appear on the network will be detected even if they don't send an unsolicited AoE Config Query response to announce their presence.  (Sometimes switches eat packets when a link comes up, for example, until a spanning tree algorithm runs for a while, so that these unsolicited announcements from targets can get lost.)

When the last user space or kernel user of an aoe-exported block device closes it, the aoe driver issues a directed AoE Query Config to that specific AoE target.  When the user runs aoe-revalidate or aoe-discover, it triggers the sending of AoE Query Config commands.

On Jan 20, 2014, at 2:56 AM, Lars Täuber <taeuber@xxxxxxx> wrote:

> Hi Ed,
> 
> does aoe "accept" the unexpected responses?
> What can be the reason that aoe issues Query Config Information Requests?
> 
> Lars
> 
> Fri, 17 Jan 2014 15:17:50 +0000
> Ed Cashin <ecashin@xxxxxxxxxx> ==> Lars Täuber <taeuber@xxxxxxx> :
>> On Jan 16, 2014, at 10:42 AM, Lars Täuber <taeuber@xxxxxxx<mailto:taeuber@xxxxxxx>> wrote:
>> 
>> Hi Ed,
>> 
>> 
>> Thu, 16 Jan 2014 09:03:14 -0500
>> Ed Cashin <ecashin@xxxxxxxxxx<mailto:ecashin@xxxxxxxxxx>> ==> <jleu@xxxxxxxx<mailto:jleu@xxxxxxxx>> :
>> The AoE initiator (the side using the storage) called "aoe" does
>> retransmit AoE write commands for aoe_deadsecs seconds.
>> 
>> what's the default value for this parameter?
>> 
>> 180.
>> 
>> When an old request gets a response after the AoE command has been retransmitted already, it is an “unexpected response”.  You can watch for those by doing a “cat” on /dev/etherd/err.
>> 
>> —
>>  Ed
> 
> 
> -- 
>                            Informationstechnologie
> Berlin-Brandenburgische Akademie der Wissenschaften
> Jägerstrasse 22-23                     10117 Berlin
> Tel.: +49 30 20370-352           http://www.bbaw.de


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