Re: Ceph distributed over slow link: possible?

[Matthias Urlichs <matthias@urlichs.de>]

Hi,
> * I don't think it's possible to control where clients go for reads -
> Ceph is pretty much optimized to the case where all nodes are in a
> single datacenter, over a more or less homogeneous network.

So, what piece(s) of code decides which replica is read from?

Note that even in the single-datacenter case, I'd want to avoid crossing
rack boundaries if my client is in the same rack as one of the possible
OSDs.

> For writes,
> though, you'd be stuck with WAN speeds no matter what, because the data
> has to go out to all replicas before the writes complete.

Hmm. Too bad; I'd be more than happy with writing to one or two replicas,
and trusting CEPH to manage the rest of the copying in the background.

-- 
-- Matthias Urlichs