From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Marusich Subject: Re: [PATCH} Add RAID devices. Date: Tue, 26 Jul 2016 00:43:16 -0700 Message-ID: <87y44ou9nv.fsf@gmail.com> References: <20160714131306.GA11566@solar> <20160723140701.GB6873@solar> <87bn1n4mld.fsf@gmail.com> <20160725211720.GA22780@solar> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Return-path: Received: from eggs.gnu.org ([2001:4830:134:3::10]:37060) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bRx1R-0005hG-6n for guix-devel@gnu.org; Tue, 26 Jul 2016 03:43:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bRx1P-0004sT-Ut for guix-devel@gnu.org; Tue, 26 Jul 2016 03:43:25 -0400 Received: from mail-pa0-x234.google.com ([2607:f8b0:400e:c03::234]:35250) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bRx1P-0004sP-KK for guix-devel@gnu.org; Tue, 26 Jul 2016 03:43:23 -0400 Received: by mail-pa0-x234.google.com with SMTP id iw10so69493361pac.2 for ; Tue, 26 Jul 2016 00:43:23 -0700 (PDT) In-Reply-To: <20160725211720.GA22780@solar> (Andreas Enge's message of "Mon, 25 Jul 2016 23:17:20 +0200") List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org Sender: "Guix-devel" To: Andreas Enge Cc: guix-devel@gnu.org, myglc2 --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Hi Andreas, Ludo's response clarified a lot of things for me. The only remaining feedback I have is that (1) to aid the reader, you should consider adding a cross-reference from "(guix) Mapped Devices" (in the part where you mention that certain modules must be added) to "(guix) Initial RAM Disk", and (2) you might want to look into using the "Auto Assembly" feature of mdadm (see below). If you've tested the changes, though, and it works, I see no reason not to commit this and enable everyone to enjoy the use of RAID arrays! :) Andreas Enge writes: > On Sat, Jul 23, 2016 at 10:43:58PM -0700, Chris Marusich wrote: >> Cool! Is it possible to use them in combination? Using the example >> From the documentation, would it possible to use LUKS to create an >> encrypted /dev/mapper/home which uses /dev/md0 instead of /dev/sda3? > > unfortunately not. This is an area where some work should be invested. > It would require to do things properly in order also. LVM support also > comes to mind. I think these devices can be staged in an arbitrarily > complex way, no? Encrypting a RAID device, or creating a RAID device > from encrypted partitions, for instance (of which the former sounds more > reasonable to me). I agree it would be a nice feature, but if your patch is working right now to enable the use of RAID, then I think it would be fine to submit your patch now and add such a feature later. >> I understand that in Linux, the device file names (e.g., /dev/sda3) can >> sometimes change unexpectedly. If they change later on, will anything >> bad happen? > > Yes, the RAID could not be assembled, and then the machine could not boot > up. But I have never experienced this kind of problem for hard disks. It occurs occasionally [1], but the fewer disks you have, the less likely you are to observe it. I wonder if you can use mdadm's "Auto Assembly" feature (see "man 8 mdadm" for details) to avoid this issue entirely? It sounds like you might not even need to specify a source device list, if the description of "Auto Assembly" is to be believed. [1] For example: https://serverfault.com/questions/140071/hard-drive-device= -names-are-different-from-one-reboot-to-another-in-ubuntu =2D-=20 Chris --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJXlxSWAAoJEN1AmhXYIkadQgkQAKVHDJCfPqXGOLaXRx5ybZkn tE/P3L0sssjdaKfyeYF+BfARyA64FQot//l7jRLdVhwbNGy1UPR1twBUte3+I2DU VXF4R/iYFOsEHogZUV87mvPY717dWybsNnMyPYBjRyjYvWsrcQohLP2FFvK30fSQ 2DEVjCO0JoUZ/ENTaNDY/3lhem6jzXKw9lI8wQ8Wln46Hvnq467CvqI3G37HrooH AXxYWmuJ6l0jf0mutudGPf2LeYziDCJXcJleSWWMst/hJbiBYbLAN5do6k8Z/z7A xKjJKPGI8/7sIfVe3vXKOoMLqOKrQFVu/Q7sg1S+FqGGDX4/x4FLDBTEQub+TiXc QIVbKcgUxuG4F9NbjWnLtgEd1X7/G9Idz9laqzVgU1rkhzmrWUW0kze1sbASztdE 6EDryvZ/lAet60GV87L7qxb2KsrgH3xZgehdDUYULIyBejIPK5cAuNeKeqLVL8wN LksFS912jsruHAfZuaaXK/ciGDUm++VBzKGR0uc/44BzvEC4dCc0CU2DEDxHm2ar wsZ4bjJrrO/yTmuCQPd7UV7xvmIfczlZI9t4zwp8aSQYJ4jSKenLjgDiW+fiREJi pykbpgl5nxloivl55q6Dq1n5kN6t3JS90ClZzx+8qKtEnaOTtI8HE5oKbKdwyZWw oDuYjLh2SbKzuD9P6OXf =elQd -----END PGP SIGNATURE----- --=-=-=--