From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout-afa67.mailout.artfiles.de ([212.72.176.67]:50273 "EHLO mailout-afa67.mailout.artfiles.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751252AbbD0IAN (ORCPT ); Mon, 27 Apr 2015 04:00:13 -0400 From: Wolfgang Mader To: Duncan <1i5t5.duncan@cox.net> Cc: linux-btrfs@vger.kernel.org Subject: Re: How to get the devid of a missing device Date: Mon, 27 Apr 2015 10:00:07 +0200 Message-ID: <1714496.4Yoe3Ejg52@discus> In-Reply-To: References: <1704142.6uN5bYeLWo@discus> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Monday, April 27, 2015 02:11:05 AM Duncan wrote: > Wolfgang Mader posted on Sun, 26 Apr 2015 20:39:34 +0200 as excerpted: > > Hello, > > > > I have a raid10 with one device missing. I would like to use btrfs > > replace to replace it. However, I am unsure on how to obtain the devid > > of the missing device. > > The devid is if the device is still active in the filesystem. If it's > missing... > > btrfs device delete missing > > That, along with a bunch of other likely helpful information, is covered > on the wiki: > > https://btrfs.wiki.kernel.org > > Specifically for that (reassemble from the wrap, too lazy to fiddle with > it on my end): > > https://btrfs.wiki.kernel.org/index.php/ > Using_Btrfs_with_Multiple_Devices#Replacing_failed_devices > > But since it was a four-device raid10 and four devices is the minimum for > that, I don't believe it'll let you delete until you device add, first. Thanks for your answer. I know the stuff of that page, but since it is possible to use btrfs replace on a missing device I wanted to try that approach. > > Of course that means probably some hours for the add, then some more > hours for the delete missing, during which you obviously hope not to lose > another device. Of course the sysadmin's backup rule of thumb applies -- > if you don't have a backup, by definition, loss of the data isn't a big > deal, or you'd have it backed up. (And the corollary, it's not a backup > until it's tested, applies as well.) So you shouldn't have to worry > about loss of a second device during that time, because it's either > backed up or the data isn't worth the trouble to backup and thus loss of > it with the loss of a second device isn't a big deal. Well, of course, there is a backup on a different machine. Its in the same room, but who has the luxury for off-site backups in a home-use setting! :) > > That page doesn't seem to cover direct replacement, probably because the > replace command is new and it hasn't been updated. But AFAIK replace > doesn't work with a missing device anyway; it's the fast way to replace a > still listed device, so you don't have to add and then delete, but the > device has to still be there in ordered to use that shortcut. (You could > try using missing with the -r option tho, just in case it works now. The > wiki/manpage is a bit vague on that point.) > > > Btw, the file system is too old for skinny metadata and extended inode > > refs. If I do a btrfs replace or a btrfs device add, must I myself > > ensure that the new features are not enables for the new device which is > > to be added? > > I don't believe there's any way to set that manually even if you wanted > to -- you don't use mkfs on it and the add/replace would overwrite > existing if you did. The new device should just take on the attributes > of the filesystem you're adding it to. Good to know. Thanks