From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Nelson Subject: Re: All-Flash Ceph cluster and journal Date: Thu, 19 Nov 2015 08:34:11 -0600 Message-ID: <564DDDE3.9050409@redhat.com> References: <564DB2A1.9080603@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49463 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758502AbbKSOeN (ORCPT ); Thu, 19 Nov 2015 09:34:13 -0500 In-Reply-To: <564DB2A1.9080603@gmail.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Mike Almateia , Ceph Development This is actually the direction newstore is heading with the newstore_min_alloc_size so that you can configure when to write into the rocksdb WAL. By default it's set to 512k, but for SSDs we will almost certainly want to go smaller. On 11/19/2015 05:29 AM, Mike Almateia wrote: > Hello. > > By now we have SSD disks with a great perfomance under O_DIRECT/O_SYNC > flags (and we recomended to use they for journal). > > Why in a All-Flash type Ceph clusters we still use journal and them put > a data into OSD? > Why we can't just write a data into OSD with O_DIRECT/O_SYNC flags, > without journal? > > Can we just switch off the journal functional for all-flash ceph clusters? >