From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Urlichs Subject: Re: Ceph distributed over slow link: possible? Date: Sat, 22 Jan 2011 11:06:31 +0000 (UTC) Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: Received: from lo.gmane.org ([80.91.229.12]:45530 "EHLO lo.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752849Ab1AVLGo (ORCPT ); Sat, 22 Jan 2011 06:06:44 -0500 Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1PgbIp-00005z-B2 for ceph-devel@vger.kernel.org; Sat, 22 Jan 2011 12:06:43 +0100 Received: from netz.smurf.noris.de ([213.95.21.43]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 22 Jan 2011 12:06:43 +0100 Received: from matthias by netz.smurf.noris.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 22 Jan 2011 12:06:43 +0100 Sender: ceph-devel-owner@vger.kernel.org List-ID: To: ceph-devel@vger.kernel.org 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