From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ric Wheeler <rwheeler@redhat.com>
Subject: Re: [PATCH] barrier support for other md/raid levels
Date: Fri, 18 Sep 2009 14:43:20 -0400
Message-ID: <4AB3D4C8.1080602@redhat.com>
References: <19123.9980.940255.937839@notabene.brown>	 <4AB372BA.6020101@redhat.com>	 <4D87015385157D4285D56CA6101072FF26C2CCB1@exchange07.valvesoftware.com>	 <4AB3D148.3060607@redhat.com> <87f94c370909181138g197be2fegd4032778ca6d3351@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Return-path: <linux-raid-owner@vger.kernel.org>
In-Reply-To: <87f94c370909181138g197be2fegd4032778ca6d3351@mail.gmail.com>
Sender: linux-raid-owner@vger.kernel.org
To: Greg Freemyer <greg.freemyer@gmail.com>
Cc: Chris Green <cgreen@valvesoftware.com>, Neil Brown <neilb@suse.de>, "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>, Mike Snitzer <snitzer@redhat.com>, Tom Coughlan <coughlan@redhat.com>, Chris Mason <chris.mason@oracle.com>
List-Id: linux-raid.ids

On 09/18/2009 02:38 PM, Greg Freemyer wrote:
> On Fri, Sep 18, 2009 at 2:28 PM, Ric Wheeler<rwheeler@redhat.com>  wrote:
>    
>> On 09/18/2009 02:19 PM, Chris Green wrote:
>>      
>>> It seems like what you'd need to robustly test barriers is some sort of
>>> barrier-supporting loopback device, which
>>> acted correctly with barriers, but had worst-case behavior without them
>>> (buffering things for random arbitrarily long periods of time,
>>> performing all operations in random order, etc).
>>>
>>>
>>>
>>>        
>> I think that it is pretty easy to get corruption (defined as fsck issues) if
>> we have non-working barriers and do power fail testing. It is a bit tricky
>> to automate that though but we are working on it,
>>
>> ric
>>      
> Ric,
>
> You are probably already using them to help automate the process, but
> if you don't know computer controlled power switches are pretty
> standard fare for computer clusters.  I'm sure Redhat's cluster team
> has some.
>
> And the cluster team may also have scripts to test things like
> unexpected power fails to one of the cluster members.  It may not be
> too hard to adjust those scripts to handle your needs.
>
> Greg
>    

We definitely have those and do similar testing. It is a matter of 
getting a good work load and automating the regression testing.

Chris's earlier test is a great starting point, HP has tests (hazard) 
that do really mean things to storage as well.

Just need to get time to get it all going :-)

ric