From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from [195.159.176.226] ([195.159.176.226]:49598 "EHLO blaine.gmane.org" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752968AbdKTV6W (ORCPT ); Mon, 20 Nov 2017 16:58:22 -0500 Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1eGu4p-0004lH-Ch for linux-btrfs@vger.kernel.org; Mon, 20 Nov 2017 22:58:03 +0100 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: Issues while doing btrfs delete missing in raid6 Date: Mon, 20 Nov 2017 21:57:47 +0000 (UTC) Message-ID: References: <20171120014344.7a5d8bd2@Vantage.cJ> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Jérôme Carretero posted on Mon, 20 Nov 2017 01:43:44 -0500 as excerpted: > While doing a test (to evaluate drives), where I'm filling a bunch of > drives in RAID6, one of the disks failed in the process. > (System with v4.14 / ECC). FWIW, see raid56 status in the status page (table and below raid56 note). https://btrfs.wiki.kernel.org/index.php/Status Basically, after the fixes in 4.12, it mostly works as long as things don't go too badly wrong, but due to the write hole and corner cases such as the checksum repair failure you ran into, it's not something people on this list can in good conscience recommend for general use, because it simply lacks the reliability people tend to want raid56 for, at least in combination with the file-integrity/checksumming features btrfs may be chosen for. The two together simply aren't as reliable as the separate features might imply they should be, and there are known to be better alternatives. Unfortunately that's likely to remain the case for awhile due to the complexity of a real fix, despite the 4.12 fixes to the worst of the problems. One reasonably performant and reliable alternative, tho it's more directly an alternative to btrfs raid10, where it's better performing due to btrfs raid10 not yet being performance optimized, is btrfs raid1 on top of two raid0s (mdraid0, for instance). -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman