Re: [Aoetools-discuss] redundant aoe storage using drbd

[Alexandre C. <a.c...@ho...>]

Le 28/09/2011 12:43, Justin Albstmeijer a écrit :
> Hi Alexandre,
>
>>> All seems to work fine and performance is acceptable.
>> Wow, I sounds really tricky to me... not sure I would do this in an
>> active-active mode like you did.
>> Can anybody confirm exporting the same block device (well... replicated
>> block devices) from 2 diffrenets servers is fair/clever/secure?
>> Does the aoe kernel module really deals with load balancing over
>> multiple targets?
> Yes the aoe module switches between the device sources every few
> seconds, you can see it with aoeping. It's the default multipath
> behavior of the aoe mudule.
Yep this makes sense in one way... it's just yet another MAC address 
from the initiator point of view.
However having aoe packets spreaded through multiples target would 
definitely break any (re-)ordering system.
I don't know if there is any case where aoe have to re-order packets but 
initiators may retransmit frames and this may (or may not) be an issue 
for an active-active setup.

I am quite interrested by this kind of setup, if you don't mind I think 
people here would like to ear more about your testings and if it works 
in production environnement.

>
>> How do you export your block device? same lvs have same shelf/slot
> numbers on both servers?
>
> Yes.
I'd like to have someone else feeling about having 2 shelves with the 
same ID exporting (replicated) block devices with the same slot number. 
Is it something the protocol can handle?

Maybe someone from Alyseo?

>
>> I'd go the safer way: active/passive redundancy.
>>> Any advise/feedback is welcome.
> Thanks for your feedback,
>
> I'll have to figure out where to leave the fail-over decision,
> - at the aoe module side if possible
> - at the qaoed/ggaoed side by adding/omitting aoe devices.
If you go for an active/passive setup, I think the target is the right 
place for the failover decision to stand (using stonith mechanism)

> The following looks like a possible failover setup
>
> https://help.ubuntu.com/community/HighlyAvailableAoETarget
>
> Justin
>
>
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Alexandre Chapellon

Ingénierie des systèmes open sources et réseaux.
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