From: "Sidorov, Andrei" Subject: Barriers Date: Mon, 13 May 2013 07:54:48 +0000 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT To: ext4 development Return-path: Received: from ironmail.arrisi.com ([216.234.147.20]:44387 "EHLO arrisi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751232Ab3EMHyv convert rfc822-to-8bit (ORCPT ); Mon, 13 May 2013 03:54:51 -0400 Content-Language: en-US Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi, I'm curious if anyone ever tried fua-only jbd? If done with fua's, there will be no cache flushes at all, thus no occasional spikes. NCQ fua journalling is potentially more efficient than cache flush. I know, stale data will be unavoidable (however unlikely) in fua-based implementation. It is a compromise between ordered,nobarrier (fs corruption is likely to happen upon power loss) and ordered,barrier (no fs corruption). Any advise on what kind of workload to test? What about having single journal per device as opposed to partition/fs? What I've found of quick look at jbd2 code, it doesn't seem to be a problem to set up single journal for several filesystems on the same device. This will give an advantage of single commit per commit interval as opposed to several commits per likely to be same interval. -- Regards, Andrei.