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Re: [Linux-cluster] GFS on AOE



On 12/07/2010 04:39 PM, Jeff Sturm wrote:
>> -----Original Message-----
>> From: linux-cluster-bounces redhat com
> [mailto:linux-cluster-bounces redhat com]
>> On Behalf Of Fabio M. Di Nitto
>> Sent: Tuesday, December 07, 2010 5:42 AM
>> To: linux-cluster redhat com
>> Subject: Re: [Linux-cluster] GFS on AOE
>>
>> The problem being that AOE (as you suspect) adds a different level of
> caching.
> 
> Note however that the AoE protocol does not specify caching, except for
> optional asynchronous writes.  (The aoe Linux module does not utilize
> asynchronous writes.)

In our testing we did have several issues with the setup described above
and trimmed down the problem to have:

node A -> controller/driver X -> harddisk
node B -> (any network block device, including AOE) -> controller/driver
X -> harddisk.

And isolated the issue to the asymmetry of the setup.

> 
> Nevertheless, the configuration suggested by the OP is unusual, and
> won't be very useful in my opinion.  Having node B rely on a hard disk
> in node A leaves node A as a single point of failure.

Yes absolutely. It does not make any sense, but for basic testing is
"good enough".


> 
> We use GFS over AoE extensively, and find it works well.  However we use
> an AoE target that runs independent of the cluster and provides
> high-availability on its own.

Yes, this is also tested and works fine. As you might have noticed in
the FAQ, we only describe the asymmetric setup as "not-working".

Fabio

> 
> -Jeff
> 
> 
> 
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