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[Sylvain Bauza <sylvain.bauza@xxxxxxxxxxxx>]

Hi John,

Le 30/04/2013 18:13, John Griffith a écrit :
> Hi Sylvain,
>
> This doc is a bit outdated and references Nova Volumes etc, however 
> the problem I think you're having is that it makes some assumptions 
> regarding knowledge of how all the components tie together and what 
> they do.  They're simply guidelines for possible configurations, 
> however given the flexibility of OpenStack and the numerous use cases 
> I've always thought this was sort of a difficult task (recommended 
> hardware configs).
>
> That being said, the Volume Group and disk portion of that doc that's 
> being discussed is in relation to your block-storage through Cinder. 
>  This is the back-end storage that you're configuring Cinder to use. 
>  The preference regarding RAID, Size etc are completely up to you, but 
> you can make some of those decisions based upon how you intend to use 
> your OpenStack deployment.
>
> For example you can just take any free disks/partitions on your Cinder 
> node, create one big LVM VG out of them (cinder-volumes) and the 
> default Cinder set up would then allocate space from this VG any time 
> you do a "cinder create".  The recommendations in the doc are geared 
> toward what would typically be required to have a functional setup, 
> the size, configuration and type of disks you use is going to vary 
> depending upon how many tenants you plan to have, how much block 
> storage you suspect they'll deploy and what kind of performance 
> they're going to require.
>
> The other thing to keep in mind is OpenStack is fully scale-out, so 
> you can start with something and as you need more storage for Cinder 
> you can add Cinder nodes with more disks/VG's.
>
> I hope that helps.
>
> John


I do agree with your point of view : it's up to the operator to define 
which Cinder backend to use, physical setup, partitioning etc.

My point was not to know which one is better, rather to say "hey, we 
tell people to use /*two*/ SATA Disks, this is pretty specific, so we 
should explain why".

If there is no clear reason to recommend 2 disks without being clear on 
how to use them, then the 2nd recommended disk is useless.

Anyway, I'm not fond of giving people /recommended hardware/, I would 
rather give people /recommended backends/, as of course hardware is 
strongly depending on the backend itself.

My 2 cents,
-Sylvain