Re: ATA over Ethernet (aoe) Experience?

["Kristian Erik Hermansen" <user=152@nabble.blu.org>]

 Cool idea, and please let us know if you implement it and the result 
works.  But I feel compelled to also point you to vmware's vmotion 
product :-) 



On 7/12/08, Kent Borg <[hidden email]> wrote: 
> Anyone here have experience with ATA over Ethernet ("aoe")? 
> 
> To be specific, here is my idea: I want to do more of that trendy 
> "server consolidation" but not have all my eggs in one basket.  So I 
> imagine having two identical physical machines, each set up to match the 
> other.  Normally I run all the VMs on one machine.  Worrying about disks 
> dying I put each VM on a pair of software raid 1 disks in that box.  But 
> how do I quickly switch to the other physical machine? 
> 
> Here is where I get clever (and ask for advice):  On the other machine I 
> do the exact same thing.  VM on a pair of software raid 1 partitions. 
> But how to sync them up? 
> 
> First, shut down the spare copy.  Only run one copy of the VM at a time. 
> 
> Second, shutdown the md device for that spare copy. 
> 
> Third, export the two physical partions via ATA over ethernet.  (Be an 
> aoe target.) 
> 
> Fourth, on the primary machine, import the two partitions via ATA over 
> ethernet.  (Be an aoe initiator.) 
> 
> Fifth, on the primary machine, add the two partitions to the raid 1 md 
> device.  Wait for the data to copy, but still keep the VM running and 
> serving whatever good stuff it does. 
> 
> 
> I haven't researched it much, but if I have dedicated gigabit ethernet 
> )or faster) and a crossover cable, and do a large MTU hack on those two 
> NICs, maybe the ATA over ethernet could mostly keep up with the local 
> disks?  Or maybe not... 
> 
> Next obvious idea would be to not ship both partitions over the ethernet 
> cable separately, but to put them together into a raid 1 pair first and 
> instead ship the md device over the cable. 
> 
> But there is something else I would like to do: run the VM on one 
> physical machine, shut it down, reverse the ATA over ethernet setup, 
> boot the VM on the other physical machine, and have the various md 
> components all happy and in synch with no replication necessary.  Doing 
> a flat collection of 4 distinct physical partitions would probably 
> work.  But if I did nested and rehanging the tree, a complete 
> replication would have to happen unless I did some hacking. 
> 
> Example. 
> 
> case 1: 
>   - yin's sda1 
>   - yin's sdb1 
>   - yang's aoe, which is 
>     - yang's sda1 
>     - yang's sdb1 
> 
> case 2: 
>   - yang's sda1 
>   - yang's sdb1 
>   - yin's aoe, which is 
>     - yin's sda1 
>     - yin's sdb2 
> 
> Is there a way to hack md internals to make the two cases boot back and 
> forth and keep the md in synch both ways? 
> 
> 
> Practical consession: maybe just running in this aoe mode while messing 
> with configurations and migrating VMs, and just run local raid 1 when 
> things are stable. 
> 
> 
> Comments? 
> 
> 
> Thanks, 
> 
> -kb 
> 
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