From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wido den Hollander Subject: Re: Looking to Use Ceph Date: Thu, 03 Jan 2013 15:38:46 +0100 Message-ID: <50E597F6.6000609@widodh.nl> References: <50E579AF.10206@sussex.ac.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp02.mail.pcextreme.nl ([109.72.87.138]:58297 "EHLO smtp02.mail.pcextreme.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752852Ab3ACOiu (ORCPT ); Thu, 3 Jan 2013 09:38:50 -0500 In-Reply-To: <50E579AF.10206@sussex.ac.uk> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: "emyr.james" Cc: "ceph-devel@vger.kernel.org" On 01/03/2013 01:29 PM, emyr.james wrote: > Hi, > > I'm thinking of starting to use ceph initially for evaluation...seeing > how it compares to our existing lustre file system. > One thing that I would like confirmation of is how ceph stores large > files. If I store a large file in CephFS is it automatically split up > into chunks with the various chunks stored and replicated automatically > across the whole cluster, or does it store the whole file as one object > on one individial OSD and then has individual replicants of the whole > file on a small number of other OSD's ? What is the typical block size > used if files are split up....can this be configured ? > Files are by default striped in 4MB blocks which are then distributed over the OSDS and replicated. A 1G file will thus result in 256 different object distributed and replicated through your cluster. You can configure the stripe-size with the "cephfs" tool on a client. Note: CephFS hasn't got the attention like RADOS and RBD got, so you might run into some weird situations. Wido > Regards, > > Emyr > > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html