From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ishtar.tlinx.org ([173.164.175.65]:53006 "EHLO Ishtar.sc.tlinx.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751726AbcK2Xvk (ORCPT ); Tue, 29 Nov 2016 18:51:40 -0500 Received: from [192.168.3.12] (Athenae [192.168.3.12]) by Ishtar.sc.tlinx.org (8.14.7/8.14.4/SuSE Linux 0.8) with ESMTP id uATNpbn8015199 for ; Tue, 29 Nov 2016 15:51:39 -0800 Message-ID: <583E1488.7090502@tlinx.org> Date: Tue, 29 Nov 2016 15:51:36 -0800 From: "L.A. Walsh" MIME-Version: 1.0 Subject: Fwd: default mount options Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: linux-xfs@vger.kernel.org Is it possible for the 'mount' man page to be enhanced to show what the defaults are? Or if that's not possible, maybe the xfs(5) manpage? Also, I'm again "unclear" on barriers. The xfs(5) man page says: "barrier|nobarrier - Enables/disables the use of block layer write barriers... this allows for drive level write caching to be enabled. Barriers are enabled by default. This seems to say that barriers are enabled. Does that mean the the barriers are implemented in the HW of the disk, or that SW adds "barriers" for disks that don't have them implemented in HW? It also says drives may enable write-caching -- but this should only be done if they support write barriers. How is this "decided"? I.e is it done "automatically" in HW? in SW? Or should the user "know"? Is this related to whether or not the drives support "state" over power interruptions? By having non-volatile "write-cache" memory, battery-backed cache, or backed by a UPS? Wouldn't SSD's be considers safe for this purpose (because their state is non-volatile?). I seem to "get" this topic periodically, but after some time passes, and upon rereading the associated manpages, I realize I'm not real clear which way is what and realize the lack of defaults being specified and whether or not SSD's and/or UPS-backed disks were safe whether barriers were present or not was still vague. Thanks! -linda