From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from [195.159.176.226] ([195.159.176.226]:32847 "EHLO blaine.gmane.org" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1755757AbdLTRae (ORCPT ); Wed, 20 Dec 2017 12:30:34 -0500 Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1eRiAJ-0000y9-OQ for linux-btrfs@vger.kernel.org; Wed, 20 Dec 2017 18:28:23 +0100 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: Unexpected raid1 behaviour Date: Wed, 20 Dec 2017 17:28:10 +0000 (UTC) Message-ID: References: <5A357909.8010206@yandex.ru> <23094.37316.66397.431081@tree.ty.sabi.co.uk> <91965e24-3b94-7334-c249-d8de5f585f29@gmail.com> <20171218194351.GA25245@polanet.pl> <7ff86029-5b0f-1d02-778a-af78c6f3e461@gmail.com> <20171219144644.GA9855@polanet.pl> <20171219204155.GB14726@polanet.pl> <20171219222308.GE14726@polanet.pl> <862f03b0-9311-09f6-ee2c-d53d35d176bd@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Austin S. Hemmelgarn posted on Wed, 20 Dec 2017 08:33:03 -0500 as excerpted: >> The obvious answer is: do it via kernel command line, just like mdadm >> does: >> rootflags=device=/dev/sda,device=/dev/sdb >> rootflags=device=/dev/sda,device=missing >> rootflags=device=/dev/sda,device=/dev/sdb,degraded >> >> If only btrfs.ko recognized this, kernel would be able to assemble >> multivolume btrfs itself. Not only this would allow automated degraded >> mounts, it would also allow using initrd-less kernels on such volumes. > Last I checked, the 'device=' options work on upstream kernels just > fine, though I've never tried the degraded option. Of course, I'm also > not using systemd, so it may be some interaction with systemd that's > causing them to not work (and yes, I understand that I'm inclined to > blame systemd most of the time based on significant past experience with > systemd creating issues that never existed before). Has the bug where rootflags=device=/dev/sda1,device=/dev/sdb1 failed, been fixed? Last I knew (which was ancient history in btrfs terms, but I've not seen mention of a patch for it in all that time either), device= on the userspace commandline worked, and device= on the kernel commandline worked if there was just one device, but it would fail for more than one device. Mounting degraded (on a pair-device raid1) would then of course work, since it would just use the one device=, but that's simply dangerous for routine use regardless of whether it actually assembled or not, thus effectively forcing an initr* for multi-device btrfs root in ordered to get it mounted properly. -- 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