From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from frost.carfax.org.uk ([85.119.82.111]:34239 "EHLO frost.carfax.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751529AbbH0R7v (ORCPT ); Thu, 27 Aug 2015 13:59:51 -0400 Date: Thu, 27 Aug 2015 17:59:47 +0000 From: Hugo Mills To: Chris Murphy Cc: carlo von lynX , Btrfs BTRFS Subject: Re: Impossible to mount two different copies of the same btrfs Message-ID: <20150827175947.GL23769@carfax.org.uk> References: <20150827173229.GA30068@lo.psyced.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kaF1vgn83Aa7CiXN" In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: --kaF1vgn83Aa7CiXN Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Aug 27, 2015 at 11:53:28AM -0600, Chris Murphy wrote: > On Thu, Aug 27, 2015 at 11:32 AM, carlo von lynX > wrote: > > Hi there. Excuse me if I didn't subscribe the list. Just wanted to > > let you know of this behavior assuming you haven't noticed it yet. > > > > When mounting two copies of the same file system from two different > > hard disks with the intention of syncing the older with the newer > > one, btrfs behaves differently from ext4: it will mount the first > > one twice rather than mounting each. I assume it has something to > > do with all UUIDs being identical, which doesn't disturb ext4 though. > > I'd say any file system that allows mount without warning when two fs > volumes with the same UUID is a bug. I vastly prefer the XFS behavior > in this regard which is warn and refusal to mount. You have to use -o > nouuid to make it happen; and then I guess there's some separate > handling to still keep the fs instances separate, but I don't know how > that works at all or how ext4 and Btrfs differ. See my other email in this thread. :) Hugo. -- Hugo Mills | You know... I'm sure this code would seem a lot hugo@... carfax.org.uk | better if I never tried running it. http://carfax.org.uk/ | PGP: E2AB1DE4 | --kaF1vgn83Aa7CiXN Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJV31ATAAoJEFheFHXiqx3kaiUQAI/eh3i+dTtBw2sqkIbLKbUm kWuN48dLHnBZMwzEDiJfA06GuCIKOk8wFyXJ8HquebtisLOGm7Aj7TgtNSM+pi9R AuQt3lgAMMa7IAweOdhnpwRiTTR7hivrNs2oReu3bqZRL8ynMLO/BDIwswXEBymm 5ajjSfHy5T/VwVBd+jgVnpDQgSQBo4SDINd+tCKi1lWBa17jREJe4BZjc1wDdV1x 8Y7agpwTJ+0FCka9tLnumRlSd8arrpnOH3Q/ETSfI0RqCimspAEw1XdfHa7TXuHN cwGtNvooxAzj5SuaV7Qt6C1YtkXv+qfZwXLFqIYKv3CfzpGkOGhg7T2Oyo04MWj7 bKtp+cu+YYcxwqRgdl0PSNimqDUj3Pj0T6N0/6i9kNMEoiL+rYqXrtH7HB4ji5aT 5C2lkAXBHcHuh6jXKc/XThbaA/uqY6WEkYPFYC/uuf2nHvw5Wbkwngx8hYWydf1c yslLHNBBrhbbKHpRfEh/yhLWrfca++L/R3P3Vc1nYP9R+bdCm/aPQkTwbj+U2SBO LBMi8mLi3E55W9gKYcICedIp1QHBqPk2kLSfeLY1Ze2SlZ7GgMN5zz69BopkYWVr b6gklICUAyGxAvDQoS75CLBKeqtenFBoo3j0+vGVXatXJbnXlVgc3Vk1DXPCaEs9 r8a/p6mvP4hJSvlmfSNw =U1Ne -----END PGP SIGNATURE----- --kaF1vgn83Aa7CiXN--