From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:54982 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754055AbbDTIPJ (ORCPT ); Mon, 20 Apr 2015 04:15:09 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1Yk6r9-0008VU-Mc for linux-btrfs@vger.kernel.org; Mon, 20 Apr 2015 10:15:03 +0200 Received: from 78-20-36-53.access.telenet.be ([78.20.36.53]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 20 Apr 2015 10:15:03 +0200 Received: from gcp by 78-20-36-53.access.telenet.be with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 20 Apr 2015 10:15:03 +0200 To: linux-btrfs@vger.kernel.org From: Gian-Carlo Pascutto Subject: Re: The FAQ on fsync/O_SYNC Date: Mon, 20 Apr 2015 10:13:47 +0200 Message-ID: References: <49296740.rPqQP4vAjc@merkaba> <20150420042731.GA20194@hungrycats.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 In-Reply-To: <20150420042731.GA20194@hungrycats.org> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 20-04-15 06:27, Zygo Blaxell wrote: >> I'm curious as to whether +C has any effect on BTRFS's durability, too. > > I would expect it to be strictly equal to or worse than the CoW > durability. In addition to the stuff pointed out, I've wondered about this: PostgreSQL full_page_writes copies 8k pages in order to prevent corruption from partial writes. But btrfs has 16k pages by default, so a corrupted FS page would corrupt more data than PostgreSQL protects. Maybe it's not an issue if the underlying HW has 512b/4k sectors, or maybe I'm misunderstanding what the respective features assume, but unless informed to the contrary I wouldn't be entirely comfortable with this. (With CoW enabled, you don't have partial writes, so the point is moot) -- GCP