[Gluster-users] Exorbitant cost to achieve redundancy??

[Jeff White]

On 02/14/2012 01:25 PM, John Mark Walker wrote:
> ----- Original Message -----
>> I'm currently fighting to get GlusterFS replica in an HPC environment
>> but the "wasting half the space" argument is hard to fight when
>> there's
>> a tight budget.  There really is no waste at all, the space is being
>> used for full server redundancy (IMHO you need server redundancy, not
>> just disk redundancy) and in some use-cases, increased performance
>> (in
>> other use-cases replica is slower).
>
> I think this gets to the heart of the matter. This is very much on our minds as we look at future roadmaps.
>
> For now, replica 2 + RAID underneath is a valid solution for the vast majority of use cases.
True, but it seems like at some point the cost of N+N just looks silly 
(think if you need 2,000 servers to get the usable space of 1,000 of them).
> There shouldn't be many cases where replica 3 is absolutely necessary - not when you utilize a decent RAID card.
> To pose the issue in a slightly different light, what would you want future behavior to be? Is erasure coding something that you view as essential in the near future?
>
> -JM
By "erasure coding" I assume you mean "some RAID 5/6-like data recovery 
with parity".  I think this should be something to investigate and see 
if it is plausible to build.  At the very least it opens GlusterFS to 
more use-cases and more design choices.